Passive Management Research Articles

Polyamide 6-Al2O3 nanoparticle composite nanofiber membranes with high solar reflectivity and human radiation transmittance for passive human body cooling

Passive radiant heat management is an energy-saving thermal radiation management technology that can improve the temperature regulation of conventional clothing in high-temperature environments. However, existing materials are either complex in structure, difficult to fabricate, or unsuitable for human application. In this study, a novel nanofiber membrane was developed that exhibits high solar reflectance and infrared transparency to human radiation, thus having an excellent radiative cooling effect. The nanofiber membrane was prepared by electrospinning polyamide (PA) 6 containing Al2O3 nanoparticles. It exhibits an average solar radiation reflectance of about 88 %, a maximum reflectance of more than 95 %, and transmittance to the human body infrared of more than 95 % and provides a cooling effect of 4–6.4 °C for outdoor objects (with convection), which results from the coaction of PA6 nanofibers and Al2O3 nanoparticles. The implementation of nanofiber membranes in clothing could not only protect wearers from high outdoor temperatures but also improve air and moisture permeability. We hope that this unique nanofiber membrane will be useful for managing thermal comfort and energy efficiency in various applications ranging from architectural materials to personal cooling solutions.

Preparation and melt-spun applications of PA6-based Poly(Amide-Ether) copolymers phase change fibers with passive temperature management

Phase change fiber, as an intelligent fiber material used in passive thermal management, can balance the temperature of the microenvironment near human skin. However, the traditional blending method makes phase change material prone to leakage during the processing and applications. Herein, this work introduces the phase change material PTMEG into the polyamide 6 (PA6) chain through melt polymerization to prepare a series of PA6-based poly(amide-ether) copolymers. Copolymers exhibit an obvious microphase separation structure, with the PA6 segments and the PTMEG segments can form independent crystalline and amorphous regions. PTMEG in copolymers through polymerization method exhibits better thermal stability compared with the blended way, which effectively solves the leakage problem of phase change materials. The copolymers can be directly melt-spun (1500 m/min) to prepare PA6-based phase change fibers. The fiber can maintain excellent mechanical properties (breaking strength of 2.12 cN/dtex). Meanwhile, the crystallization enthalpy and melting enthalpy of the PTMEG in the fiber are 10.59 J/g and 12.44 J/g, respectively. The thermal management time of the fiber in the hot environment is 349 s, and the maximum temperature difference is lower 5.6 ℃ from the PA6 fiber. In addition, the exothermic duration in a cold environment is 536 s, and the maximum temperature difference is higher 1.1 °C from the PA6 fiber. Meanwhile, the thermal enthalpy of the fiber remained stable (fluctuation within 2 %) after 20th thermal cycles, and the loss rate is less than 2 % after washing at 25 ℃, 50 ℃ and 90 ℃. The fiber exhibits good thermal stability, water washability and cyclic stability. Preparation of high enthalpy polymers directly by copolymerization will provide new ideas for phase change fibers for apparel.

Experimental and numerical investigation on a hybrid high-temperature downhole thermal management system integrating liquid cooling and phase change material

The downhole electronics must operate in an extremely thermal environment for several hours. Previous researches have proved that passive thermal management systems (PTMSs) are able to protect downhole electronics over extended durations. However, conventional PTMSs commonly suffer from a significant thermal resistance between the electronics and phase change materials (PCM), which restricting the efficient heat transfer to the PCM and consequently reducing the effective operating time. In this study, a hybrid thermal management system (HTMS) integrating liquid cooling and phase change thermal energy storage technique was proposed to enhance the internal heat transfer performance of downhole electronics and extend the operation duration. An active heat transfer channel was established between the electronics and PCM through liquid cooling system, and thus the generated heat was efficiently transferred and stored in PCM. The thermal performance of the proposed HTMS was investigated both experimentally and numerically. The accuracy of the numerical model was validated through experimental results, with a deviation lower than 6 %. The experimental results show that the temperature difference between the heat source and the heat storage module (HSM) was reduced by up to 51.9 °C, and the workable time was increased by up to 166 mins compared to the system without liquid cooling. The proposed HTMS exhibits superior heat transfer performance, which contributes to achieving a longer effective operation duration and holds extensive and profound application prospects in the field of thermal management for downhole electronic devices.

Qualitative analysis of the coupling effect of fluid velocity distribution in microchannels on the performance of water-cooling lithium-ion batteries system

ABSTRACT Lithium-ion batteries are the direct power sources of electric vehicles, but their high heat flux density restricts their development. Microchannel heat sinks (MCHS) can assist in heat dissipation to overcome this. The distribution of fluid velocity among microchannels has a considerable effect on the performance of MCHS for a water-cooling lithium-ion batteries system. In this paper, a new microchannel heat sink with high depth to width aspect ratio is proposed and the influence of four different aspect ratios on the distribution of fluid velocity among microchannels and heat transfer performance of MCHS was numerically studied by computational fluid dynamics (CFD). The results showed that at the same inlet flow rate, the larger the aspect ratio of the microchannels, the better the uniformity of the internal fluid velocity. The heat performance of microchannel structures with four different aspect ratios for a water-cooling lithium-ion batteries is further investigated experimentally. Compared with the simulation results of the fluid velocity distribution, the coupling effect between the fluid velocity distribution in the microchannels and the heat dissipation performance of a water-cooling lithium-ion batteries is analyzed. The results fully demonstrated that a larger aspect ratio of the microchannels results in a better heat dissipation performance on the surface of the lithium-ion batteries. Optimizing the aspect ratio of the microchannels to facilitate a relatively uniform velocity distribution to improve heat dissipation performance of the water-cooling system may be a key factor to be considered, which provides a new idea for passive thermal management of batteries.

Spatiotemporal Information, Near-Field Perception, and Service for Tourists by Distributed Camera and BeiDou Positioning System in Mountainous Scenic Areas

The collaborative use of camera near-field sensors for monitoring the number and status of tourists is a crucial aspect of smart scenic spot management. This paper proposes a near-field perception technical system that achieves dynamic and accurate detection of tourist targets in mountainous scenic areas, addressing the challenges of real-time passive perception and safety management of tourists. The technical framework involves the following steps: Firstly, real-time video stream signals are collected from multiple cameras to create a distributed perception network. Then, the YOLOX network model is enhanced with the CBAM module and ASFF method to improve the dynamic recognition of preliminary tourist targets in complex scenes. Additionally, the BYTE target dynamic tracking algorithm is employed to address the issue of target occlusion in mountainous scenic areas, thereby enhancing the accuracy of model detection. Finally, the video target monocular spatial positioning algorithm is utilized to determine the actual geographic location of tourists based on the image coordinates. The algorithm was deployed in the Tianmeng Scenic Area of Yimeng Mountain in Shandong Province, and the results demonstrate that this technical system effectively assists in accurately perceiving and spatially positioning tourists in mountainous scenic spots. The system demonstrates an overall accuracy in tourist perception of over 90%, with spatial positioning errors less than 1.0 m and a root mean square error (RMSE) of less than 1.14. This provides auxiliary technical support and effective data support for passive real-time dynamic precise perception and safety management of regional tourist targets in mountainous scenic areas with no/weak satellite navigation signals.

Application of the International Standards for noise insulation assessment of a metamaterial-based ventilated window

In recent years, acoustic metamaterials (AMMs) have been developed to create more ergonomic designs that can be integrated into the built environment. For instance, embedding metamaterials in windows has facilitated effective ventilation and sound insulation. Presently, European standards provide specific guidelines for evaluating the insulation properties of façades, enabling the characterisation of both active and passive noise management solutions to ensure a healthy indoor environment. However, these standards primarily focus on closed partitions, limiting their applicability to noise management open systems. This study employs the ISO 10140 measurement method to assess a vertical metamaterial-based partition, namely an acoustic metawindow (AMW) unit, that, when open, allows noise insulation and ventilation contemporarily. The standardised level difference (Dn,e) is used to assess the performance of the open AMW unit's noise insulation. The results demonstrate the applicability of ISO 10140 for assessing an open AMW unit's performance, showcasing a Dn,e,w = 27 dB in the frequency range 1000-5000 Hz and an improvement over an open standard window ranging from 3 to 15 dB. This initial exploration could pave the way for more inclusive regulations considering ventilated sound-insulating devices as vertical partitions in the built environment and more comprehensive assessment methods for AMMs-based ventilated systems.

Psychometric properties of the multifactor leadership questionnaire when used in early-career pharmacists with provisional registration

BackgroundThe Multifactor Leadership Questionnaire (MLQ) is a validated instrument used to explore participants' perceptions of leadership and the Outcomes of leadership, participants' evaluation of and satisfaction with leadership and willingness to put in extra effort. The factor structure of MLQ varies across studies. The aim was to explore the psychometric properties of the MLQ for early-career pharmacists rating their preceptor's leadership. MethodsThe MLQ was administered to provisionally registered pharmacists during the final half of their 1 year of supervised practice. Confirmatory and Exploratory Factor Analysis (CFA & EFA) and Structural Equation Modeling (SEM) were used to analyse the data. ResultsResponses were obtained from 430 participants (25 % of all Australian pre-registration pharmacists at the time). CFA demonstrated that the original 9-factor model and a range of previously published models were poor fit for the data. EFA revealed that a good fit was a model with 4 factors named: Passive laissez-faire, Strategic visionary, Personalized, and Active management by exception. Passive laissez-faire and Active management by exception were consistent with previously published models. The Strategic visionary and Personalized factors were interpreted as 2 forms of transformational leadership that includes the provision of rewards depending on performance. A SEM of MLQ sub-scales predicting Outcomes of leadership explained 90.3 % of variance. Personalized leadership was highly predictive (β = 0.743, P < 0.001) while the three other factors had negligible effects. ConclusionThe psychometric analyses demonstrated overlap of the original 9-factors. A more parsimonious 4-factor model fit the data well.

An open-loop and closed loop based passive thermal management techniques applicable to photovoltaic systems

Photovoltaic (PV) technology adoption in recent years has experienced significant growth due to its inherent advantages over alternative technologies. Nevertheless, there is a concern regarding performance deterioration due to high operating temperatures. Various thermal management methods have been studied to address this issue, each having its own advantages and disadvantages. Hence, a comprehensive review aimed at developing effective passive cooling techniques was undertaken and two techniques were finalized for outdoor testing viz. natural circulation loop based cooling (PV-NCL) and evaporative cooling (PV-EVP). Though the former version could drop module temperature by 7.4 °C–13.9 °C (Power output increment in the range of 3.5 %–6.7 %), this improvement was not sustained throughout the day due to factors such as flow resistance within the loop and a lack of convective cooling in the vicinity of the cooler. Subsequent experiments confirmed that loop resistance played a dominant role in this phenomenon. Additionally, concerns about water circulation in PV-NCL were resolved through a comparison with water duct-integrated PV. On the other hand, the innovative gravity-assisted water flow for evaporation method (PV-EVP) yielded more promising results, with a power output enhancement ranging from 3.7 % to 11.5 %. However, considering the in-field operational issues, PV-NCL with a modified design will likely be the best technique.

Nano-Enhanced Graphite/Phase Change Material/Graphene Composite for Sustainable and Efficient Passive Thermal Management.

Passive battery thermal management systems (BTMSs) are critical for mitigation of battery thermal runaway (TR). Phase change materials (PCMs) have shown promise for mitigating transient thermal challenges. Fluid leakage and low effective thermal conductivity limit PCM adoption. Furthermore, the thermal capacitance of PCMs diminishes as their latent load is exhausted, creating an unsustainable cooling effect that is transitory. Here, an expanded graphite/PCM/graphene composite that solves these challenges is proposed. The expanded graphite/PCM phase change composite eliminates leakage and increases effective thermal conductivity while the graphene coating enables radiative cooling for PCM regeneration. The composite demonstrates excellent thermal performance in a real BTMS and shows a 26% decrease in temperature when compared to conventional BTMS materials. The composite exhibits thermal control performance comparable with active cooling, resulting in reduced cost and increased simplicity. In addition to BTMSs, this material is anticipated to have application in a plethora of engineered systems requiring stringent thermal management.

From Efficiency to Effectiveness: Practical Strategies and Mindset Shifts in Graduate Time Management

Time management plays a crucial role in academic achievement and personal growth during the graduate stage. This article explores practical strategies and mindset shifts in graduate time management from the perspectives of efficiency and effectiveness. Graduates not only need to improve the speed and quantity of task completion but also focus on the quality and value of results. The article analyzes challenges faced by graduates in time management, such as multitasking, balancing academics and life, and unclear goals, and proposes practical strategies including setting clear goals, using time management tools, working in segments and focusing on time blocks, and arranging rest reasonably. Additionally, graduates should shift from doing more to doing more valuable things and from passive management to active design to achieve higher academic results and personal development.

Versatile Ultrahigh‐Output Bilayer Hydrogel for Electricity Generation and Passive Cooling

AbstractThe gradient concentration in nature has garnered significant attention as a promising source for energy harvesting. Researchers have explored various methods to harness electricity from gradient‐concentration‐induced flows, including evaporation‐driven nanogenerators and humidity‐gradient‐based power generators. However, their low current and power density are the main obstacles toward practical applications. Herein, a Bilayer Hydrogel Electricity Generator (BHEG) is presented to enable efficient energy harvesting through the synergy between ion gradient concentration and galvanic effects. A BHEG unit employing identical materials for both electrodes demonstrates an open‐circuit voltage of 0.7 V and a short‐circuit current of 4.34 mA—surpassing the currently reported average by over 73 times—and achieves a maximum power density of 72.2 mW m−2. Moreover, another BHEG unit using Zn─C electrode materials exhibit an open‐circuit voltage of 1.86 V and a short‐circuit current of 92 mA. Furthermore, the versatility of the BHEG extends beyond power generation, effectively providing passive thermal management for electronics, resulting in a maximum temperature reduction of ≈20 °C. Consequently, the study contributes insights into the design and fabrication of efficient hydrogel‐based power generators, providing a promising avenue for leveraging natural‐flow‐induced energy for various applications.

A Sensor Probe with Active and Passive Humidity Management for In Situ Soil CO2 Monitoring.

Soil CO2 concentration and flux measurements are important in diverse fields, including geoscience, climate science, soil ecology, and agriculture. However, practitioners in these fields face difficulties with existing soil CO2 gas probes, which have had problems with high costs and frequent failures when deployed. Confronted with a recent research project's need for long-term in-soil CO2 monitoring at a large number of sites in harsh environmental conditions, we developed our own CO2 logging system to reduce expense and avoid the expected failures of commercial instruments. Our newly developed soil probes overcome the central challenge of soil gas probes-surviving continuous exposure to soil moisture while remaining open to soil gases-via three approaches: a 3D printed housing (economical for small-scale production) following design principles that correct the usual water permeability flaw of 3D printed materials; passive moisture protection via a hydrophobic, CO2-permeable PTFE membrane; and active moisture protection via a low-power micro-dehumidifier. Our CO2 instrumentation performed well and yielded a high-quality dataset that includes signals related to a prescribed fire as well as seasonal and diel cycles. We expect our technology to support underground CO2 monitoring in fields where it is already practiced and stimulate its expansion into diverse new fields.

Passive battery thermal management and thermal safety protection based on hydrated salt composite phase change materials

Lithium-ion batteries (LIBs) are progressing towards higher energy densities, extended lifespans, and improved safety. However, battery thermal management systems are facing increased demand owing to high-rate charging and discharging, dynamic operating conditions, and heightened thermal safety concerns. Therefore, this paper proposes a novel composite phase change material (CPCM) comprising Na2SO4-10H2O as the core phase change material (PCM) and expanded graphite as the thermal conductivity enhancer. The CPCM offers high latent heat, superior thermal conductivity, and a two-stage temperature control function for battery thermal management and safety. The optimal mass CPCM ratio, determined through comprehensive characterization and thermal property tests, resulted in a melting point of 29.05°C, latent heat of 183.7 J.g−1, and high thermal conductivity of 3.926 W.m−1.K−1. During normal LIB operations, the CPCM efficiently absorbs and transfers heat, reducing the peak LIB temperature from 66 to 34°C at 15°C ambient temperature during a 3.7C high-rate discharge. Under dynamic conditions, the peak temperatures across the three cycles were consistently controlled at 36.7, 36.4, and 35.8°C, respectively. In a thermal runaway state, the thermochemical heat storage of hydrated salt dehydration effectively slowed LIB temperature increase, delaying the time to reach 130°C by 187 s. Suppression of the temperature rise outside the CPCM, combined with an extended dehydration plateau of up to 320 s, prevented the occurrence and propagation of thermal runaway in the battery.

Compatibility and conflict between environmentalist and occupational identities in Northern California’s forests

ABSTRACT This study examines the relationship between occupational identity and attitudes toward environmentalism, using interviews with 55 workers in northern California, including loggers, governmental employees, and members of environmental organizations. The results suggest that attitudes toward environmentalism are shaped by and reflective of the ways participants identify with their work, which is itself a product of both internal (community) and external (stigma) forces. In particular, this relationship appears in the types of environmental knowledge possessed and preferred by participants, debates about active versus passive management, and long-lasting historical narratives form the timber wars. Ultimately, workers are fairly flexible in their attitudes toward the landscape, and they are willing even to shift their own occupational identity over time, as new forest issues emerge. However, they are often more rigid when it comes to perspectives of others, and this poses some challenges for the future of collaboration in western forest management.

Distribution strategy of flexible phase change materials for pouch battery thermal management considering temperature non-uniformity

Flexible composite phase change materials (CPCMs) have been extensively studied in the thermal management of cylindrical lithium-ion batteries and proven to have a good cooling effect. However, passive cooling of pouch lithium-ion batteries with severe uneven temperature distribution has not received the attention it deserves. The thermal management of pouch battery based on passive cooling of flexible PCMs considering the heat-generating structure of pouch batteries needs to be further studied. Herein, CPCMs with different thermal conductivity were prepared, and four different distribution modes of CPCMs, including partial coverage and complete coverage, were applied to thermal management of pouch battery. Results indicated that the maximum temperature (Tmax) and maximum temperature difference (ΔTmax) can be kept separately within 35 °C and 5 °C in the passive thermal management of a single battery except upper coverage at discharge rate of 5C, and the middle coverage (case B) showed excellent temperature control in partial coverage cases. Equally noteworthy was that the increase in thermal conductivity increased the ΔTmax in partial coverage cases, while showing the opposite trend for full coverage (case ABC). Furthermore, only passive cooling of pouch battery pack did not meet the safety requirements under the discharge rate cycle of 5C. Under the active–passive combination mode, case B can control the Tmax (32.22 °C) and ΔTmax (4.69 °C) within a safe range, which was superior to case ABC (Tmax = 35.53 °C, ΔTmax = 5.04 °C). This conclusion provides technical support for the pouch battery to seek economic, stable and efficient thermal management.

Analisis Komparatif Kinerja Reksadana Saham &amp; Reksadana Indeks Berdasarkan Metode Sharpe, Treynor, dan Jensen

Mutual fund get investors attention cause the risk rate are smaller than the other investment instrument, its because mutual fund are managed by a reliable party on investment called professional management. Different types of mutual funds offer different ranks of risk and return. This study use secondary data and independent sample t-test analysis technique with computer assist program SPSS 13 to compare performance between equity fund that use active management strategies and mutual fund index that use passive management strategies. Test result show that performance between equity fund and mutual fund index measured using sharpe, treynor and jensen methods are don’t have significant performance differences. So investors are free to invest their money on equity fund instrument or mutual fund index, cause its return and risk are similar.

Investigating superior performance by configuring bimetallic electrodes on fabric triboelectric nanogenerators (F-TENGs) for IoT enabled touch sensor applications

Fabric Triboelectric Nanogenerators (F-TENGs) are increasingly becoming more significant in wearable monitoring and beyond. These devices offer autonomous energy generation and sensing capabilities, by replacing conventional batteries in flexible wearables. Despite the substantial effort, however, achieving high output with optimal stability, durability, comfort, and washability poses substantial challenges, so we have yet to see any practical commercial uses of these materials. This study focuses on output and investigates the impacts of mono and bimetallic composite fabric electrode configurations on the output performance of F-TENGs. Our findings showcase the superiority of bimetallic configurations, particularly those incorporating Copper (Cu) with Nickel (Ni), over monometallic (Cu only) electrodes. These configurations demonstrate remarkable results, exhibiting a maximum instantaneous voltage, current, and power density of ∼ 199 V (a twofold increase compared to monometallic configurations), ∼22 μA (a threefold increase compared to monometallic configurations), and 2992 mW/m², respectively. Notably, these bimetallic configurations also exhibit exceptional flexibility, shape adaptability, structural integrity, washability, and mechanical stability. Furthermore, the integration of passive component-based power management circuits significantly enhances the performance capabilities of the F-TENGs, highlighting the essential role of power management circuits and electrode selection in optimizing F-TENGs. In addition, we have developed a complete IoT-enabled touch sensor system using CuNi-BEF EcoFlex layered F-TENGs for precise detection of soft and hard touches. This advanced system enhances robotic functionality, enabling nuanced touch understanding essential for precision tasks and fostering more intuitive human-machine interactions.

The Active Versus Passive Investing Debate: Evidence From the 2018-2023 Market Cycle

The paper investigates the research question: Which investment management style, active or passive, produced better risk-adjusted performance from January 1, 2018, to December 31, 2023 (Prondzinski, 2010)? The comprehensive time period was further subdivided into two periods: January 2020 – May 2023, the Pandemic period, and March 2022 – December 2023, the interest rate hiking period without any interest rate cuts. The study tested twenty-seven hypotheses derived from this research question for the specified periods addressed. The study, consisting of 27 statistical tests, found that on a risk-adjusted basis, the Sharpe ratios of active indices (proxies for active management) significantly exceeded the passive indices (proxies for passive management) in nine of the periods tested) (Prondzinski, 2010).

The intrinsic flame retardant multifunctional composite phase change material with phosphorus pentoxide for battery thermal safety system

The temperature distribution has severely affected the performance of lithium-ion battery modules in electric vehicles (EVs), composite phase change material (CPCM) with excellent temperature controlling function as a passive battery thermal management system is essential to ensure the safety of battery module. In this study, the polyethylene glycol phosphate ester (PEGP) has been synthesized by esterification of phosphorus pentoxide and polyethylene glycol through the reaction of PEGP and melamine (MA), the network crosslinking structure has been built to greatly improve the anti-leakage performance. The flame-retardant CPCM containing PEGP/expanded graphite /epoxy resin/MA (PPEM) has been successfully designed and prepared. The results indicate that PPEM2 containing 20 wt% melamine and 7 wt% epoxy resin exhibit excellent antileakage and prominent flame retardant properties comprehensively. It should be noted that the peak heat release rate of PPEM2 has been reached to 352.41 KW/m2, which is obviously decreased by 47.55 % comparing with pure PEG. The main reason is that the grafting flame retardant elements (P) and melamine onto polyethylene glycol molecular chain by chemical reaction. In addition, it can maintain the operating temperature below 36 °C at 23 A discharge current. The battery module with PPEM2 can transfer the heat timely and promptly, exhibiting outstanding flame-retardant effect to avoid thermal runaway. With these prominent performances, this intrinsic flame-retardant CPCM can not only exhibit an excellent thermal management effect but also provide a promising approach to inhibit the thermal runaway propagation.

Optimization of cutting parameters in manufacturing of polymeric materials for flexible two-phase thermal management systems

Abstract This research study with an extensive literature review represents a comprehensive multi-criteria analysis for optimizing the cutting parameters in the manufacturing of flexible two-phase passive thermal management systems (FTP-TMS) using thermoplastic materials. Recognizing the critical role of thermoplastics in FTP-TMS due to their inherent flexibility and lightweight properties, this research focuses on the precision cutting of polypropylene, polyethylene, and polyvinyl chloride using CO2 laser technology. The study is structured into three distinct phases. Initially, an experimental setup was conducted to cut 2 mm thick thermoplastic materials with varying power and cutting speed parameters. Subsequently, the SWARA method was employed to weight the criteria, followed by the application of seven different multi-criteria decision-making (MCDM) methods for optimization. The final phase involved a detailed analysis of the outputs, including ranking, correlation, and sensitivity analyses. The findings indicate that cutting polypropylene with a 90 W power setting and a speed of 15 mm s−1 yields the most optimal results. This study fills a significant gap in the existing literature by providing a dedicated analysis for thermoplastics in FTP-TMS manufacturing. The insights gained are pivotal for standardizing manufacturing practices and enhancing the design and fabrication of flexible thermal management solutions, offering substantial benefits to sectors like electronics, aerospace, and automotive industries.