Passive Mode Research Articles

Photovoltaic-integrated advancements for sustainable water production: Developing and evaluating an enhanced hybrid solar desalination system

The global water crisis demands innovative solutions, and solar desalination is a promising avenue. However, traditional systems often suffer from low yields. This study centres on the development, assessment, and economic feasibility of the Enhanced Hybrid Solar Still (EHSS), a pioneering approach to sustainable clean water production. Integrating photovoltaic technology, the EHSS targets a minimum daily output of 15 L/m2. Computational Fluid Dynamics (CFD) simulations guide the design optimisation, identifying an optimal configuration of 4 mm basin thickness, a 2 mm glass cover thickness, and a 56° slope. The EHSS is a single component that comprises of passive operation and advanced components integration, including monocrystalline solar panels, a hybrid MPPT inverter, a deep cycle battery, and a custom water heater, to enhance the yield. The EHSS undergoes a comprehensive assessment encompassing distillate quality, efficiency, and economic viability. In passive mode operation (solely using solar radiation), clean water yields range from 4.7111 L/m2·day to 2.1309 L/m2·day. Transitioning to active mode operation (employing photovoltaics and additional components) significantly enhances yields to a range of 19.7 L/m2·day. Impressively, the EHSS consistently delivers an average daily water yield of 16.85 L/m2, and also its purity meets World Health Organization standards for drinking water. The PV systems exhibit a charge rate of 14.28 % per hour on clear days and 9 to 11 % per hour on semi-cloudy days, with the battery depleting at 16.66 % per hour at 70 °C operational temperature. Comparative analysis against traditional systems showcases an efficiency increase from 25.61 % to an outstanding 64.01 % for the optimised EHSS (PV system and appurtenances). A strong correlation (coefficient of 0.9701) between experimental and simulation results indicates robust relationships. Over a 20-year lifespan, cost analysis reveals a per-litre cost of 0.0892 US dollars for the EHSS, compared to 0.0374 US dollars for traditional systems. Extended lifespans further underscore the economic feasibility of the EHSS, emphasizing its role in providing sustainable clean water solutions.

Seasonal Performance Characterization of a Gen3 Particle-Based Concentrating Solar Plant With a Spatially Resolved Transient Thermal Storage Model

Particle-based Gen3 Concentrating Solar Power (CSP) can be paired with high-temperature power cycles (>700 °C) and can have built-in long duration (≥10 hours) thermal energy storage if the working particles are stored properly in thermal energy storage bins. Although high-temperature and long-duration thermal energy storage can mitigate daily intermittencies in solar irradiation, seasonal variability in local meteorological conditions can still have a significant impact on the overall performance of CSP systems. Aside from daily cloud coverage affecting incident solar radiation, wind speed and ambient temperature are also significant variables regarding system heat attenuation, component efficiency, and overall solar conversion efficiency. In this work, we present simulation results for a Gen3 CSP prototype system in operation over four weeks throughout the year in Albuquerque, NM. The meteorological conditions are taken directly from the TMY3 data at the Albuquerque International Sunport, where the hourly Direct Normal Irradiation (DNI), wind speed, and ambient temperature are of particular interest. An investigation of the sensitivity of individual components like storage and ducting to the local meteorological conditions is provided and extended to the overall performance of the CSP system. The results from this study show that the particle inlet temperature at the particle-to-sCO2 heat exchanger can change as fast as 30 °C/min under standard operation in a passive mode.

Pre-existing structural control on the recent Holuhraun eruptions along the Bárðarbunga spreading center, Iceland

The active rift zones in Iceland provide unique insight into the geodynamic processes of divergent plate boundaries. The geodynamics of Iceland are studied intensively, particularly, by geophysical methods sensitive to active and/or visible structures such as earthquake seismic and Synthetic Aperture Radar observations or aerial photographs. However, older and less active structures, that may exert a strong control on the presently active geodynamics, are often buried beneath recent volcanic or sedimentary deposits and are—due to their passive mode—overseen by the typical geophysical investigations. Aeromagnetic surveys provide spatial information about subsurface magnetization contrasts relating to both active and inactive structures. However, the aeromagnetic data in Iceland were collected in the 1970-80s and are relevant only to large-scale regional rift studies. With the availability of reliable drones and light-weight atomic scalar sensors, high-quality drone magnetic surveys can provide an unprecedented spatial resolution of both active and passive structures of rift systems as compared to conventional airborne surveys. Here, we present the results of a drone-towed magnetic scalar field and scalar gradiometry study of the north-northeast trending Bárðarbunga spreading center to the north of the Vatnajökull ice cap, Iceland. Our results provide new information about the structural complexity of rift zones with evidence of densely-spaced, conjugate and oblique faults throughout the area. Evidence is shown of a hitherto unknown and prominent east-northeast trending fault structure that coincides with the northern tip of the main eruption edifice of the 1797 and 2014-15 Holuhraun volcanic events. We suggest that this pre-existing structure controlled the locus of vertical magma migration during the two Holuhraun events.

Study of Thermal Management of Li‐Ion Batteries with an Encapsulated Phase‐Change Material and Internal Liquid Channels

ANSYS Fluent is used to simulate battery thermal management (BTM). A new concept design of cooling techniques with encapsulated phase‐change material (PCM) and internal coolant channels is proposed. In this study, the passive mode of cooling (MODEL‐A: without internal cooling) and proposed design incorporating with internal liquid channels (MODEL‐B, MODEL‐C, MODEL‐D, MODEL‐E, and MODEL‐F) are considered. The upper section of the chamber is the starting point for the melting progression, which then moves toward the downward lower section of the chamber. Two design concept cooling techniques are used: straight and spiral coolant channels. At the point 15 mm, the PCM gets initiated melting at 1000 s for MODEL‐A (no coolant channels), and only a heating up of PCM is observed for MODEL‐B and MODEL‐C. Faster initiation of melting period over and above 35 mm position and at higher position point 55 mm, which reaches a liquidus temperature 328.6 K at below 2000 and 1000 s, respectively. MODEL‐D, MODEL‐E, and MODEL‐F show the PCM temperature reduction across the axial length due to the presence of coolant channels. The spiral channels can maintain the liquid fraction for longer periods, which allows liquid to contribute to the sustainability of a longer‐lasting thermal storage system.

Soft Artificial Muscle Based on Pre-Detwinned Shape Memory Alloy Spring Actuator Achieving High Passive Assistive Torque for Wearable Robot.

For designing the assistive wearable rehabilitation robots, it is challenging to design the robot as energy efficient because the actuators have to be capable of overcoming human loads such as gravity of the body and spastic torque continuously during the assistance. To address these challenges, we propose a novel design of soft artificial muscle that utilizes shape memory alloy (SMA) spring actuators with pre-detwinning process. The SMA spring was fabricated through a process called pre-detwinning, which enhances the linearity of the SMA spring in martensite phase and unpowered restoring force, which is called passive force. The fabricated SMA spring can contract >60%. Finally, the soft wearable robot that can assist not only the gravitational torque exerted on the elbow by passive force, but also the elbow movements with active force was designed with a soft artificial muscle. A soft artificial muscle consists of the bundles of pre-detwinned SMA springs integrated with the stretchable coolant vessel. The stiffness of the muscle was measured as 1125 N/m in martensite phase and 1732 N/m in austenite phase. In addition, the muscle showed great actuation frequency performances, the bandwidth of which was measured as 0.5 Hz. The proposed wearable mechanism can fully compensate the gravitational torque for all the angles in passive mode. In addition, the proposed mechanism can produce high torque up to 3.5 Nm and movements in active mode.

Multimode Control Strategy for Robotic Rehabilitation on Special Orthogonal Group SO(3)

Robot-assisted rehabilitation for three-degree-of-freedom joints, such as hip and ankle, is significant for patients with motor function injuries. The control of such robots involves attitude control. To adapt to different disease stages, multi-mode hybrid control is considered to be one of the best choices. Passive mode is based on trajectory tracking control, while active mode is based on field-based assist-as-needed (AAN) control. The key to AAN control is the solution of the closest attitude point. However, the attitude point belongs to a special orthogonal group SO(3), and its topology is completely different from Euclidean space, which causes difficulties to the solution. Both passive and active control methods are affected by the inaccuracy of model parameters and external disturbances. Therefore, this paper proposes a multi-mode hybrid control method on SO(3). First, the expressions of trajectory tracking and contour tracking errors are proposed. To solve the contour tracking error, a feedback linearization algorithm based on sliding surface was used. A radial basis function (RBF) neural network was used for adaptive compensation. Subsequently, a controller for different modes was designed and its stability was analysed. Experiments were conducted using a hip exoskeleton, and the results verified the effectiveness of the proposed control method.

Comparison of the Laser Generation Parameters in the Coherent and in the Standard Incoherent Passive Mode Locking Regime

Comparison of the Laser Generation Parameters in the Coherent and in the Standard Incoherent Passive Mode Locking Regime

Taking Titan’s Boreal Pole Temperature: Evidence for Evaporative Cooling in Ligeia Mare

From 2004 to 2017, the Cassini RADAR recorded the 2.2 cm thermal emission from Titan’s surface in its passive (radiometry) mode of operation. We use this data set to investigate the seasonal evolution of the effective temperature sensed by the microwave radiometer in two regions in the northern pole of the satellite: the sea Ligeia Mare, and its nearby solid terrains. We find that despite the arrival of summer at the end of the mission, the effective temperature of Ligeia Mare decreased by almost 1 K, while that of the solid region slowly increased until 2017 by 1.4 ± 0.3 K. These observations, as well as the lag in summer warming observed by Cassini’s Composite Infrared Spectrometer, can be explained by evaporative cooling in both the solid and liquid surfaces after the vernal equinox. It therefore supports the idea that the northern polar terrains are wet. Using an ocean circulation model, we show that the cooling of the sea surface should initiate convection in the sea’s interior, ultimately cooling the whole liquid column sensed by the Cassini radiometer and thus decreasing the temperature at depths even long after the evaporation period has ceased. Overall, this work highlights the key role of methane hydrology in controlling the surface and submarine temperatures in the boreal polar regions of Titan.

Application of Regularization Methods in the Sky Map Reconstruction of the Tianlai Cylinder Pathfinder Array

The Tianlai cylinder pathfinder is a radio interferometer array to test 21 cm intensity mapping techniques in the post-reionization era. It works in passive drift scan mode to survey the sky visible in the northern hemisphere. To deal with the large instantaneous field of view and the spherical sky, we decompose the drift scan data into m-modes, which are linearly related to the sky intensity. The sky map is reconstructed by solving the linear interferometer equations. Due to incomplete uv coverage of the interferometer baselines, this inverse problem is usually ill-posed, and regularization method is needed for its solution. In this paper, we use simulation to investigate two frequently used regularization methods, the Truncated Singular Value Decomposition (TSVD), and the Tikhonov regularization techniques. Choosing the regularization parameter is very important for its application. We employ the generalized cross validation method and the L-curve method to determine the optimal value. We compare the resulting maps obtained with the different regularization methods, and for the different parameters derived using the different criteria. While both methods can yield good maps for a range of regularization parameters, in the Tikhonov method the suppression of noisy modes are more gradually applied, produce more smooth maps which avoids some visual artefacts in the maps generated with the TSVD method.

Investigation on the construction of teaching case base in medical genetics.

Medical genetics is a basic medical course that discusses the diagnosis, prevention and treatment of diseases in relation with genetic factors. This course requires students who have abilities of strong logical thinking, independent thinking, problem analyzing and solving. Single "cramming" teaching is difficult to mobilize students' autonomous learning, and hardly achieves teaching effect of medical genetics. Teaching of case-based discussion breaks passive teaching mode in traditional class. The teacher throws out typically clinical cases. The students prepare materials around relevant problems of cases, and carry out class discussion. Then, key and difficult points of the course are integrated in teaching and learning interaction, which reaches a remarkable effect of teaching. Since 2013, the teaching and research group has carried out teaching of case-based discussion in undergraduates majoring in clinical medicine. In this paper, we screen and sort clinical cases on the basis of course teaching plan and case-based discussion in the teaching of medical genetics. The cases are summarized into 8 chapters in teaching case base, which basically cover the teaching of disease genetics and clinical genetics.The construction of teaching case base in medical genetics has realized the deep integration of clinical cases and teaching. Students can understand and master important and difficult points of teaching in a more intuitive way, which is helpful to stimulate students' innovative thinking, improve students' learning interest and class participation.

Ammonia combustion using hydrogen jet ignition (AHJI) in internal combustion engines

The application of ammonia and hydrogen in internal combustion engines (ICE) is a promising zero-carbon technology. This paper investigates ammonia combustion in ICE using hydrogen multiple-injection jet-ignition (MIJI). The experiment was conducted on a single-cylinder heavy-duty engine with a compression ratio of 17 and a cylinder bore of 123 mm. In the passive jet ignition mode, the minimum hydrogen energy ratio for stable operation of the ammonia-hydrogen engine was 15 %. Using H2 active jet ignition could improve the combustion stability significantly. It was found that engine performance was gradually improved by H2 injection strategy in order of single-injection, double-injection to triple-injection. The triple-injection strategy could achieve a more ideal distribution of ammonia-hydrogen mixture: the first injection forms a homogeneous mixture to increase fuel reactivity; the second injection creates a stratified hydrogen mixture, facilitating rapid flame propagation; the third injection forms a relatively rich mixture in the jet chamber conducive to spark ignition. Through the optimization of the hydrogen injection strategy and spark timing, stable combustion (COV = 1 %) and high thermal efficiency (ITE = 42.5 %) in ammonia-hydrogen engines were achieved, with a minimum hydrogen energy ratio less than 3 %.

I do and I understand: A virtual reality-supported collaborative design-assessing activity for EFL students

Instead of learning in a passive learning mode or aimlessly exploring VR scenarios, a collaborative design-based VR learning environment has great potential for developing classrooms. Through personal knowledge construction in a collaborative design-based learning (CDBL) environment, this study combines CDBL and VR technology to motivate students to build VR projects and practice speaking English in rich contexts through learning by design; students gradually generate knowledge from design experience and sufficient practice. Peer assessment was further introduced to enhance timely evaluation and reflection. Therefore, this study proposed a VR-supported collaborative design-assessing activity. 113 Chinese seventh-graders participated in a quasi-experiment to evaluate the effectiveness of this method. Compared to the collaborative design-assessing (CDA) activity, the results demonstrated that students in the VR-supported collaborative design-assessing (VR-CDA) activity greatly enhanced their English-speaking performance, collaboration tendency, and critical thinking awareness while lowering their English learning anxiety. In contrast to the VR-supported collaborative design (VR-CD) activity, however, the VR-CDA group activity did not significantly improve students’ English-speaking performance. The interview results proved that the students in the VR-CDA group were highly motivated to learn English because of the innovative classroom instruction. They also enjoyed designing the projects collaboratively, posting assessments, and self-reflection.

Within-session Reliability of fNIRS in Robot-assisted Upper-limb Training.

Functional near-infrared spectroscopy (fNIRS) seems opportune for neurofeedback in robot-assisted rehabilitation training due to its noninvasive, less physical restriction, and no electromagnetic disturbance. Previous research has proved the cross-session reliability of fNIRS responses to non-motor tasks (e.g., visual stimuli) and fine-motor tasks (e.g., finger tapping). However, it is still unknown whether fNIRS responses remain reliable 1) in gross-motor tasks, 2) within a training session, and 3) for different training parameters. Hence, this study aimed to investigate the within-session reliability of fNIRS responses to gross-motor tasks for different training parameters. Ten healthy participants were recruited to conduct right elbow extension-flexion in three robot-assisted modes. The Passive mode was fully motor-actuated, while Active1 and Active2 modes involved active engagement with different resistance levels. FNIRS data of three identical runs were used to assess the within-session reliability in terms of the map- (R2) and cluster-wise (Roverlap) spatial reproducibility and the intraclass correlation (ICC) of temporal features. The results revealed good spatial reliability (R2 up to 0.69, Roverlap up to 0.68) at the subject level. Besides, the within-session temporal reliabilities of Slope, Max/Min, and Mean were between good and excellent (0.60 < ICC < 0.86). We also found that the within-session reliability was positively correlated with the intensity of the training mode, except for the temporal reliability of HbO in Active2 mode. Overall, our results demonstrated good within-session reliability of fNIRS responses, suggesting fNIRS as reliable neurofeedback for constructing closed-loop robot-assisted rehabilitation systems.

Experimental study on collaborative enhancement of led heat dissipation characteristics by pulsating heat pipe and heat pipe

The objective of this research is to experimentally evaluate the specific impact of a collaborative heat sink composed of gravity heat pipes (GHP) and pulsating heat pipes (PHP) on the thermal efficiency of LED light sources. The heat sink developed in this experiment is designed to improve the thermal management system, ensuring that LED operate within a safe temperature range, which is crucial as the performance of LED is directly affected by their junction temperature. An HP-PHP collaborative heat sink was employed in the experiment, where PHP served as heat dissipating fins to enhance its thermal performance, while HP handles the majority of the heat transfer tasks. The results showed that under forced convection conditions, the HP-PHP collaborative heat sink can increase the maximum thermal power capacity of LED to 192 W. The HP-PHP collaborative heat sink can reduce the substrate?s temperature to below 70.5 ?C in passive mode when the LED input power does not exceed 96 W. Additional experimental results show that the minimum thermal resistance of the collaborative heat sink is 0.19 K/W under natural-convection conditions, under forced convection conditions, this value drops to 0.15 K/W, which still lower than the non-collaborative heat sink. These results demonstrate that the contact thermal resistance between HP and PHP significantly enhances the thermal performance of the collaborative heat sink. Therefore, this collaborative type of heat sink is an effective method for cooling high power LED.

Stoneley wave detection by acoustic Interferometry: Estimation of shear velocity of a geological formation

Both active and passive full waveform acoustic loggings (FWAL), complemented by a flow log, were conducted in a borehole of an experimental site located in the Cher region (France).. The acoustic tool used for the FWAL experiments is a flexible monopole tool holding a pair of piezoelectric receivers and a magnetostrictive transducer. The tool was modified to perform both active and passive FWAL. For passive acoustic logging, several runs were recorded to obtain a set of acoustic noise sections. As the noise is simultaneously recorded by two receivers of the tool, an interference noise section was elaborated by correlating or deconvolving the pair of signals and then summing these pairs of acoustic traces at each depth. This procedure, which can be interpreted as an interferometry analysis, points out the presence of low-frequency waves identified as Stoneley waves. The velocity and RMS amplitude of the Stoneley wave were computed at each depth. It is shown that: 1- the Stoneley wave velocity obtained in passive mode can be used to estimate the shear velocity of the formation, 2- the RMS amplitude and velocity variations of the Stoneley waves are strongly correlated with the variations of the flowmeter.

Study of Extrude Aluminum Alloy LED Bulb in a Passive Mode of Cooling System with a Different Array of Fin Structure

Nowadays, the world is running behind power generation as well as power saving. In the lighting industry, the L.E.D. bulb is used for lighting purposes. The main problem faced by the world is heat dissipation from a heat sink by active or passive cooling. The system accessories enhance the overall cost by using active cooling. This paper studied that it has been used to reduce the overall cost of L.E.D. bulbs by increasing the heat transfer rate concerning increasing heat transfer coefficient. It needs to understand the various parameters such as porosity, heat transfer rate, laminar flow, density, and heat transfer modes to achieve the above-desired result. Their application is for street lights, gardens, mall parking, and bulging decorative lights. The cross-shape fin array is a suitable replacement with porosity of more than 0.85 for a proper swirl during the cooling time for an active cooling system for an existing bulb.

Comparative assessment of indirect cabinet solar dryers in various operating modes versus direct cabinet dryers: A techno-economic analysis

A cost-effective indirect cabinet-type solar dryer was designed and developed to remove the moisture in green peas until their moisture content reaches 14–15 % with minimal energy supplied from external sources. The green peas were placed beneath the absorber plate of the modified solar cabinet dryer (MSCD) thereby preventing its exposure to direct sunlight. The performance of MSCD was assessed at three different air velocities and was compared with a conventional solar cabinet dryer (CSCD) operated in passive mode. Experimentation showed that when hot air from the upper chamber of MSCD was fed to its lower chamber at 0.0406 kg/s, the dried green peas were free from shrinkage, uneven drying, and browning. However, when hot air was fed to the lower chamber of MSCD at 0.00585 kg/s and 0.027 kg/s the dehydrated green peas underwent shrinkage. At the same time, the green peas dried in CSCD underwent shrinkage, uneven drying, and browning despite its higher efficiency (about 13.5 %) and shorter span (2 h and 30 min) taken for drying when compared to MSCD. Hence, CSCD and MSCD operated at an air velocity of 0.00585 kg/s, and 0.027 kg/s was found to be not suitable for dehydrating green peas. The efficiency of MSCD when hot air from the upper chamber was fed to its lower chamber at 0.0406 kg/s was 10.64 % and the payback period was 0.47 years.

Generation of pulse bursts with controllable number of pulses and of spectral broadening directly at the laser output from a km-long Yb-doped all-fiber laser

In this work, we study the pulse burst regime of a fiber laser, which allows generating packets of multiple pulses whose number can be precisely controlled by modifying the polarization state by means of two retarder plates (QWR, HWR). The proposed experimental scheme is a highly energetic Yb-doped all-fiber ring pulsed laser operating in the 1064 nm wavelength region and using a nonlinear polarization rotation (NPR)-based passive mode locking technique. Raman scattering effects can be found by increasing pump power to achieve the formation of up to four Stokes, resulting in a spectral broadening over more than 200 nm.

Off-site prefabricated hybrid façade systems

The residential sector is responsible for the largest share of global energy consumption, while the existing building stock in Europe is relatively old. This issue, in combination with the low rate of new constructions, highlights the necessity for deep renovation of existing buildings to reach NZEB standards. At the same time, in the last decades, off-site prefabricated solutions have gained popularity in the building market, allowing the reliable and effective integration of diverse components and reducing the total renovation cost and occupants’ disturbance. The current study describes three all-in-one “Plug &amp; Play” prefab renovation solutions and their assessment in terms of thermal, static, acoustic, and fire performance. The assessing performance is selected depending on their incorporated element as well as the national regulations of the country where the renovation solution is going to be installed. The assessment aims to ensure their characteristics’ satisfaction with the European and national requirements. In parallel, the assessment identifies the accurate behaviour of prefab façade systems both in passive and active mode and improves/optimises any possible design drawbacks.

Non-Equilibrium Nitrate Detection in Ionophore-Based Solid-Contact Ion-Selective Electrodes

Ion-selective electrodes (ISE’s) have benefits for solution-phase detection and quantification of ions, such as ease of operation, low cost, and high throughput compared to, e.g., ion chromatography or mass spectrometry methods. ISE devices are traditionally operated under zero-current conditions, where analyte ions passively exchange across a selective membrane barrier, yielding a Nernstian response after equilibration of Coulombic and chemical driving forces across the membrane. However, this passive mode of operation can require long equilibration times and lead to drift, for example due to electrolyte leakage and pH impacting the membrane and reference electrode. In recent years, non-equilibrium detection techniques have been of growing interest, where the ISE signal is obtained under applied electrical signal. However, the majority of this work has been devoted to cation sensing, with relatively few studies examining anion ISEs under active electrical actuation. Agricultural expansion and the corresponding uptick in application of supplemental nitrogen to soil has led to an increased demand for technologies to measure anions like nitrate – both from a production and regulation standpoint. In this work, we employ galvanostatic polarization of solid-contact ISEs as a non-equilibrium nitrate detection method. Our investigation involves coating electrodes with a redox-active charged polymer to act as a transduction layer to convert ionic to electronic signal, followed by solvent casting of a polymeric ion-selective membrane. We examine the impact of repeated rapid charging and discharging ISE electrode stacks on measurement time and stability. We compare the metrics derived from this technique to conventional open-circuit measurements using the same device. We identify benefits for this mode of operation using established nitrate membrane materials (e.g. nitrate ionophore VI membrane cocktail) that address some of the typical limitations of these conventional materials and we discuss opportunities for further refinement.