Search

We developed a novel amphiphilic material, arginine-arginine (RR)-bile acid (BA). RR-BA selectively binds to aSN in Parkinson’s disease and boosts aSN amyloidogenesis through a mechanism of electrostatic binding-hydrophobic condensation.

Recently, lubricant-impregnated surfaces (LIS) have emerged as a promising condenser surface by facilitating the removal of condensates from the surface. However, LIS has the critical limitation in that lubricant oil is depleted along with the removal of condensates. Such oil depletion is significantly aggravated under high condensation heat transfer. Here we propose a brushed LIS (BLIS) that can allow the application of LIS under high condensation heat transfer indefinitely by overcoming the previous oil depletion limit. In BLIS, a brush replenishes the depleted oil via physical contact with the rotational tube, while oil is continuously supplied to the brush by capillarity. In addition, BLIS helps enhance heat transfer performance with additional route to droplet removal by brush sweeping. By applying BLIS, we maintain the stable dropwise condensation mode for > 48 hours under high supersaturation levels along with up to 61% heat transfer enhancement compared to hydrophobic surfaces.

Condensation frosting causes serious economic and safety problems in many industrial applications. Recently, lubricant-impregnated surfaces (LIS) have been attracting much interest with their excellent anti-frosting ability. The facilitated removal of drops due to the low contact angle hysteresis of LIS has been suggested as the frosting suppression mechanism. Here, we demonstrate a hitherto-unexplored microscale frosting suppression mechanism on LIS by investigating microscopic condensation and freezing dynamics on LIS by varying the viscosities of the lubricants. Based on the ice propagation model, we show that the frosting propagation is suppressed on LIS with a low viscosity oil where the coalescence of droplets is promoted by the presence of oil. On the contrary, the coalescence between droplets is interrupted on LIS with a high viscosity oil, which facilitates the frost propagation. The criteria for the delay of condensation frosting were explained based on the competition between the lubricant drainage time and the drop growth time scale. Finally, we verify that microscopic frosting suppression mechanism of LIS persists up to macroscopic level by demonstrating that LIS is effective in suppressing condensation frosting on heat exchangers.

Superhydrophobic (SHPo) surfaces can provide high condensation heat transfer due to facilitated droplet removal. However, such high performance has been limited to low supersaturation conditions due to surface flooding. Here, we quantify flooding resistance defined as the rate of increase in the fraction of water-filled cavities with respect to the supersaturation level. Based on the quantitative understanding of surface flooding, we suggest effective anti-flooding strategies through tailoring the nanoscale coating heterogeneity and structure length scale. Experimental verification is conducted using CuO nanostructures having different length scales combined with hydrophobic coatings with different nanoscale heterogeneities. The proposed anti-flooding SHPo can provide a ∼130% enhanced average heat transfer coefficient with ∼14% larger supersaturation range for droplet jumping compared to a previous CuO SHPo. The proposed anti-flooding parameter and the scalable SHPo will help develop high-performance condensers for real-world applications operating in a wide range of supersaturation levels.

Energy recovery ventilators (ERV) have become popular in Korea for their use in minimizing heat loss in ventilation and maintaining indoor air quality (IAQ). The performance of ERV systems is determined by laboratory tests under prescriptive indoor and outdoor conditions. Typically, a fixed heat recovery efficiency of the ventilation system is used in building energy simulations. In this study, in order to analyze the heat recovery efficiency of an ERV under actual operating conditions, long-term field measurements were performed in a residential building in the winter. The results showed that the enthalpy heat recovery efficiencies fluctuated between 25% and 70% depending on the outdoor conditions. The sensible heat recovery efficiencies were between 30% and 65% and were proportional to the temperature difference between indoors and outdoors. The heat exchange efficiency of ERV was not constant but varied according to changes of indoor and outdoor conditions under actual operating conditions. A simulation method was used to analyze the effect of the ERV's variable heat exchange efficiency on heating energy demand in the heating season. Two cases were analyzed. Case 2 analyzed the variable heat exchange effectiveness of the ERV based on the field measurements. Case 1 examined the fixed effectiveness proposed by the manufacturer. Simulation results showed that the heating energy demand in Case 2 was 69% higher than that in Case 1. This means that the heating energy demand may be underestimated if the heat exchange efficiency of the ventilation system is assumed to be constant in the simulation.

A gravity-assisted heat pipe called a two-phase closed thermosyphon (TPCT) is an efficient thermal device that transfers a large amount of heat at a relatively small temperature difference using the phase-change process. Promoting dropwise condensation on a condenser wall of a TPCT promises an increase in the effective thermal conductance of that device. Acetone and ethanol have been widely used for heat pipe applications as working fluids. Still, they pose a limitation in promoting dropwise condensation using typical hydrophobic coatings due to their lower surface energies. Recent works have shown that lubricant-impregnated surfaces (LIS) can promote dropwise condensation of low-surface-tension fluids, but no studies proved the effectiveness of the surfaces in TPCT applications. This study experimentally achieves dropwise condensation of acetone and ethanol within a TPCT using the LIS surface. We demonstrate heat transfer enhancement of a TPCT by examining temperature uniformity, condenser and evaporator heat transfer coefficients (HTCs), and overall and partial thermal resistances. We demonstrated that the LIS condenser increased the condenser HTC by 220% and decreased the overall thermal resistance of the TPCT by 44% compared to filmwise condensation. Our work also revealed a strong dependence of working fluid viscosity on dropwise condensation stability and heat transfer enhancement by comparing the two working fluids, acetone, and ethanol. This work presents the opportunity for improving thermal performance in heat pipes and applications that rely on the condensation of low-surface-tension fluids, such as HVAC, refrigeration, and organic Rankine cycle.

We present the dynamic heat transfer analysis of condensed droplets growing and coalescing on hydrophobic (HPo) and superhydrophobic (SHPo) surfaces using a full 3D numerical simulation. In the model, two water droplets surrounded by fully-saturated water vapor grow on a horizontal surface through condensation until they coalesce together. The dynamic changes in the interfacial areas, temperature distributions and heat flux through each interface were analyzed. The effects of vapor phase temperature distribution, parasitic thermal resistance and surface flooding on the heat transfer rate are also quantified. The results show that a relatively high heat transfer rate through solid–vapor interface on SHPo partially compensates the low heat transfer rate through solid–liquid interface. The parasitic thermal resistance of the suggested SHPo may reduce the heat transfer performance over 30%. When the flooding occurs on HPo, the heat transfer rate rapidly decreases below a half of the value obtained at the beginning of coalescence. This work shows the importance of the heat transfer analysis considering dynamic changes in the interfacial area and resulting 3D temperature distributions, and will help develop the optimal condensation heat transfer surfaces.

A two-phase closed thermosyphon (TPCT), also called a gravity-assisted heat pipe, is an efficient heat transfer device that exploits boiling and condensation phase-change phenomena to transport large amounts of heat. Recently, jumping droplet condensation on a well-designed superhydrophobic (SHPo) surface has shown superior condensation heat transfer coefficient (HTC), exceeding ~380% and ~30% over conventional filmwise and dropwise condensation, respectively. However, SHPo surfaces within TPCTs have shown much lower HTCs than expected, and the exact cause of this has not been investigated yet. Here, we experimentally explored the effects and limitations of a SHPo surface in a TPCT by visualizing the internal flow patterns and condensation behavior according to heat flux. We constructed a TPCT device capable of visualizing the inside and fabricated a SHPo surface on a condenser wall of the TPCT. We revealed two important condensation characteristics that limit the condenser HTC of the SHPo surface and the TPCT's heat transfer performance. At high heat fluxes (≥ 90 kW/m2), the repetitive liquid collision led to an early flooding transition of the surface and a stepwise decrease in the condenser HTC. At low heat fluxes (

A two-phase closed thermosyphon (TPCT) is a passive heat transfer device that transfers heat from one point to another by two-phase fluid circulation. Dropwise condensation on a hydrophobic surface, where discrete droplets grow on a condenser surface, promises higher condensation heat transfer coefficients (≈40–70 kW/m2⋅K) than conventional filmwise condensation. Recent researchers have investigated the effect of dropwise condensation on the heat transfer performance of a TPCT. However, their measured condenser heat transfer coefficients (

Thermal interface materials (TIMs) with high thermal conductivity, fluidic characteristics, and surface wettability are crucial for the effective thermal management of high-power electronics. Gallium-based liquid metal (LM) can be a candidate for obtaining the purposes due to their thermo-physical properties. Several studies attempted to further increase the thermal conductivity of composites by adding conductive fillers. However, these efforts have been limited due to the oxidation and solidification issues at high vol% of fillers. In this work, we apply three strategies to obtain the enhanced thermal conductivity while maintaining the fluidity: 1) suppressing Ga-induced oxidation, 2) reducing the matrix-fillers interfacial resistance, and 3) forming additional heat-pathways within the LM matrix. An oxide-free ultrasonication-assisted particle internalization method has been developed, in which the copper nanoparticles (Cu NPs) are incorporated into the gallium-indium-tin (GaInSn) LM matrix. The fabricated composite shows ~180% enhancement of thermal conductivity (~64.8 Wm−1K−1) with only 4 vol% of nano-fillers compared to the untreated GaInSn. In the droplet impacting test, the synthesized GaInSn/Cu NPs composite presents almost identical spreading diameters with the untreated one, which confirms the maintained fluidity. The predicted thermal conductivity using the theoretical model, calculating the measured cluster fraction, is well-matched to the experimental data, which clarifies that the nanoparticle clusters created effective heat-pathways. A high-quality interface with a silicon substrate is confirmed by the X-ray photoelectron spectroscopy, demonstrating the presence of a thin-film Ga2O3 adhesion layer. In the cooling performance test, the developed TIM provides over 20% lower hot-spot temperature than that of the grease-type TIM at high heat flux regime (>150 W/cm2), showing excellent thermal stability over 230 cycles of acceleration test. This work will help develop high-performance TIMs, especially for high power density semiconductor applications.

The first main goal of this article is to give a new metrization of the Mukherjee--Varadhan topology, recently introduced as a translation-invariant compactification of the space of probability measures on Euclidean spaces. This new metrization allows us to achieve our second goal which is to extend the recent program of Bates and Chatterjee on localization for the endpoint distribution of discrete directed polymers to polymers based on general random walks in Euclidean spaces. Following their strategy, we study the asymptotic behavior of the endpoint distribution update map and study the set of its distributional fixed points satisfying a variational principle. We show that the distributdion concentrated on the zero measure is a unique element in this set if and only if the system is in the high temperature regime. This enables us to prove that the asymptotic clustering (a natural continuous analogue of the asymptotic pure atomicity property) holds in the low temperature regime and that the endpoint distribution is geometrically localized with positive density if and only if the system is in the low temperature regime., 61 pages

Surface fouling by oil is a significant engineering issue by degrading the performance of various energy systems. Recently, it has been shown that nanostructured surfaces with the proper wettability can mitigate surface fouling against various types of organic or inorganic matter in aqueous environments. However, their effectiveness in suppressing surface fouling is questionable against low surface tension bio-oils, particularly when they are present in the form of emulsified oils. Here, we show that a surface fouling on the metallic substrate can be mitigated by nanostructuring the substrate, followed by additional surface treatment. With hydrophobization of nanostructured substrate, oil-fouling is reduced up to ∼ 48 % due to the reduced surface energy, although emulsified oil still sticks to the surface. Furthermore, with additional infusion of low surface tension lubricants, oil-fouling is significantly suppressed up to ∼ 88 % due to non-sticking property of the lubricant-infused substrate even to emulsified oils. Also, it is found that surface fouling is strongly dependent on the temperature due to the change of emulsion property with the temperature, which should be taken into account in practical settings. By proposing a practical solution to minimizing surface fouling by emulsified bio-oils, we believe that our results can help address a critical fouling issue in energy systems utilizing bio-oils.

Promoting dropwise condensation on condensers has the potential to significantly improve cooling and heat recovery performance of two-phase closed thermosyphons (TPCTs). If it is well designed, the dropwise condensation can provide an order of magnitude higher heat transfer coefficient than filmwise condensation of conventional metal condensers. The thermal design of an ideal dropwise condensing surface is so important in the rationale for the advantage of dropwise condensation in the TPCTs. However, the effect of the hydrophobic promoter thickness on the thermal characteristics of the TPCT and its optimal value are still unclear. Here, we develop a unified model framework for the TPCT with the dropwise condenser and investigate how much the dropwise condensation can improve the thermal performance of the TPCT. As the hydrophobic promoter for the TPCT, we proposed a nanoscopically smooth Teflon-based hydrophobic coating on theoretical insights, experimentally evaluated its condensation heat transfer, and then developed its dropwise model with high accuracy by combining a recent dropwise model with the optimized parameters. Subsequently, the developed model was unified with the TPCT model to investigate the thermal characteristics of the TPCT system and the effect of the promoter thickness. The model results show that the Teflon-coated condenser with a thin thickness (≤ 10 nm) can significantly reduce the overall thermal resistance of the TPCT by up to 4.5 times compared to filmwise condensation. However, an increase in film thickness limited the performance enhancement of the TPCT due to the dominant thermal resistance through the film. By considering both the durability and the thermal resistance of the TPCT, we suggested the optimal Teflon film thickness as approximately 60 nm. This work provides physical insights and guidelines to obtain ideal TPCTs combined with dropwise condensers.

Purpose : The purpose of this study was to investigate the effects of flexibility and foot pressure on stretching exercise of hamstring muscle with and without pelvis neutral position. Methods : This study was performed on 30 subjects. Thirty subjects were divided into two group; hamstring passive stretching exercise with pelvis neutral position(n

A series of donor-acceptor (D–A) polymers with regioregularly incorporated a thieno[3,4-b]thiophene as a π-bridge between electron donor and electron acceptor segments were successfully synthesized for the first time. The optical, thermal, and electrochemical properties of the D–A polymers with the thieno[3,4-b]thiophene as a π-bridge were characterized by UV/vis spectroscopy, thermogravimetric analysis, and cyclic voltammetry measurements. They exhibited low energy bandgap because of extended π-conjugation length and increased electron density through conjugated polymer backbones. Moreover, they showed suitable HOMO and LUMO energy levels for photovoltaic applications. The bulk heterojunction organic photovoltaic devices based on the D–A polymers with the regioregularly incorporated thieno[3,4-b]thiophene segment exhibited about 10% higher power conversion efficiency (PCE) than the D–A polymer with thienyl segment as a π-bridge due to enhanced light harvesting ability and excellent nanoscale network. This study implies that the D–A polymers with the regioregularly incorporated thieno[3,4-b]thiophene segment as a π-bridge can achieve high PCE through structural modification of the polymers.

We introduce a thin (

The regioregular p-type copolymer PBDTTT-C-T composed of TT-BDT-TT-BDT repeating units (TT = thieno[3,4-b]thiophene, BDT = benzo[1,2-b:4,5-b′]dithoiphene) and perfectly controlled TT orientation was synthesized. The optical, thermal, and electrochemical properties of the regioregular PBDTTT-C-T were characterized and compared with the random PBDTTT-C-T without structural regioregularity. The regioregular PBDTTT-C-T showed lower optical bandgap (1.55 eV) and higher degree of crystallinity compared to the random PBDTTT-C-T. The inverted bulk heterojunction PSCs based on the regioregular PBDTTT-C-T exhibited a power conversion efficiency as high as 7.79%, which is 19% higher than the random PBDTTT-C-T-based PSCs. It was found that the improved photoabsorption and increase in charge carrier mobility due to high regioregularity of conjugated polymer backbones and effective ordering between polymer chains are the most likely reasons for enhancement of power conversion efficiency in PSCs.

The aim of this review is to look at the future of occupational accidents by analysing a Finnish Delphi and a British scenario study on the future of occupational safety and health. We then present occupational injury trends from all around the world: Europe, Asia, Australia and New Zealand, Africa, and North America. The connection between economic booms and occupational injury rates was analysed on the basis of five studies from Europe and the United States. We also briefly assess violence at the workplaces. Then we hypothesize on the future trends of occupational accidents. Based on a review of the literature, we draw three conclusions. The first concerns the development of occupational injuries in post-industrialized countries. The second addresses the increase of occupational injuries in industrialized countries. The third conclusion suggests that violence at workplaces will increase in service societies.

The efficient water harvesting from air-laden moisture has been a subject of great interest to address world-wide water shortage issues. Recently, it has been shown that tailoring surface wettability can enhance the moisture harvesting performance. However, depending on the harvesting condition, a different conclusion has often been reported and it remains unclear what type of surface wettability would be desirable for the efficient water harvesting under the given condition. Here we compare the water harvesting performance of the surfaces with various wettability under two different harvesting conditions–dewing and fogging, and show that the different harvesting efficiency of each surface under these two conditions can be understood by considering the relative importance of the water capturing and removal efficiency of the surface. At fogging, the moisture harvesting performance is determined by the water removal efficiency of the surface with the oil-infused surfaces exhibiting the best performance. Meanwhile, at dewing, both the water capturing and removal efficiency are crucial to the harvesting performance. And well-wetting surfaces with a lower barrier to nucleation of condensates exhibit a better harvesting performance due to the increasing importance of the water capture efficiency over the water removal efficiency at dewing.

The purpose of the study is to develop a finite element model based on 3D bone structural images of Micro-CT and to analyze the stress distribution for the osteoporosis mouse femora. In this study, results of finite element analysis show that the early osteoporosis of mouse model decreased a bone density in trabecular region; however, the bone density in cortical region increased., {"references":["B. V. Rietbergen, et al., \"A new method to determine trabecular bone elastic properties and loading using micromechanical finite-element models,\" J Biomech, 28, 1995, pp. 69-81.","M. Joshua, B. Steven, \"Bone strength at the distal radius can be estimated from high-resolution peripheral quantitative computed tomography and the finite element method,\" Bone 42, 2008, pp. 1203-1213.","J. Y. Rho, et al., \"Relations of mechanical properties to density and CT numbers in human bone,\" Med Eng Phys, 17, 1995, pp. 347-355.","T. L. Mueller, et al., \"Non-invasive bone competence analysis by high-resolution pQCT: an in vitro reproducibility study on structural and mechanical properties at the human radius,\" Bone, 44(2), 2009, pp. 364-371.","X. S. Liu, et al., \"High resolution peripheral quantitative computed tomography can assess microstructural and mechanical properties of human distal tibial bone,\" J Bone Miner Res, 25(4), 2010, pp. 746-756.","H. M. Macdonald, et al., \"Age-related patterns of trabecular and cortical bone loss differ between sexes and skeletal sites: A population-based HR-pQCT study,\" J Bone Miner Res, 26(1), 2011, pp. 50-62.","H. M. Macdonald, et al., \"Changes in trabecular and cortical bone microarchitecture at peripheral sites associated with 18 months of teriparatide therapy in postmenopausal women with osteorosis,\" Osteoporosis international, 22, 2010, pp. 357-362.","R. Rizzoli, et al., \"Effects of strontium ranelate and alendronate on bone microstructure in women with osteoporosis,\" Osteoporosis international, 23, 2012, pp. 305-315.","S. A. Jamal, et al., \"Effect of nitroglycerin ointment on bone density and strength in postmenopausal women,\" J Am Med Assoc., 305(8), 2011, pp. 800-807.\n[10]\tS. Hansen, et al., \"Differing effects of PTH 1-34, PTH 1-84, and zoledronic acid on bone microarchitecture and estimated strength in postmenopausal women with osteoporosis: An 18-month open-labeled observational study using HR-pQCT,\" J Bone Miner Res, 28(4), 2013, pp. 736-745."]}

On superhydrophobic (SHPo) surfaces, either of two wetting states-the Cassie state (i.e., nonwetted state) and the Wenzel state (i.e., wetted state)-can be observed depending on the thermodynamic energy of each state and external conditions. Each wetting state leads to quite a distinctive dynamic characteristic of the water drop on SHPo surfaces, and it has been of primary interest to understand or induce the desirable wetting state for relevant thermofluid engineering applications. In this study, we investigate how the wetting state of microstructured SHPo surfaces influences the water-harvesting performance via dewing by testing two different patterns, including posts and grates with varying structural parameters. On grates, the observed Cassie wetting state during condensation is well described by the thermodynamic energy criteria, and small condensates can be efficiently detached from the surfaces because of the small contact line pinning force of Cassie droplets. Meanwhile, on posts, the observed wetting state is dominantly the Wenzel state regardless of the thermodynamic energy of each state, and the condensates are shed only after they grow to a sufficiently large size to overcome the much larger pinning force of the Wenzel state. On the basis of the mechanical force balance model and energy barrier consideration, we attribute the difference in the droplet shedding characteristics to the different dynamic pathway from the Wenzel state to the Cassie state between posts and grates. Overall, the faster droplet shedding helps to enhance the water-harvesting performance of the SHPo surfaces by facilitating condensation on the droplet-free area, as evidenced by the best water-harvesting performance of grates on the Cassie state among the tested surfaces.

We report our hydrodynamic and energy analyses of droplet coalescence on water repellent surfaces including hydrophobic, superhydrophobic and oil-infused superhydrophobic surfaces. The receding contact angle has significant effects on the contact line dynamics since the contact line dissipation was more significant during the receding mode than advancing. The contact line dynamics is modeled by the damped harmonic oscillation equation, which shows that the damping ratio and angular frequency of merged droplets decrease as the receding contact angle increases. The fast contact line relaxation and the resulting decrease in base area during coalescence were crucial to enhance the mobility of coalescing sessile droplets by releasing more surface energy with reducing dissipation loss. The superhydrophobic surface converts ∼42% of the released surface energy to the kinetic energy via coalescence before the merged droplet jumps away from the surface, while oil-infused superhydrophobic and hydrophobic surfaces convert ∼30% and ∼22%, respectively, for the corresponding time. This work clarifies the mechanisms of the contact line relaxation and energy conversion during the droplet coalescence on water repellent surfaces, and helps develop water repellent condensers.

On superhydrophobic (SHPo) surfaces, either of two wetting states—the Cassie state (i.e., nonwetted state) and the Wenzel state (i.e., wetted state)—can be observed depending on the thermodynamic energy of each state and external conditions. Each wetting state leads to quite a distinctive dynamic characteristic of the water drop on SHPo surfaces, and it has been of primary interest to understand or induce the desirable wetting state for relevant thermofluid engineering applications. In this study, we investigate how the wetting state of microstructured SHPo surfaces influences the water-harvesting performance via dewing by testing two different patterns, including posts and grates with varying structural parameters. On grates, the observed Cassie wetting state during condensation is well described by the thermodynamic energy criteria, and small condensates can be efficiently detached from the surfaces because of the small contact line pinning force of Cassie droplets. Meanwhile, on posts, the observed wet...