Undesirable Transfer Research Articles

Decoupling mass transport and electron transfer by a double-cathode structure of a Li-O2 battery with high cyclic stability

<h2>Summary</h2> Aprotic lithium-oxygen (Li-O₂) batteries have attracted extensive attention due to their ultrahigh theoretical energy density. However, slow and undesired electron transfer during cathodic reactions causes low cyclic stability in these batteries. Here, we demonstrate that O₂ mass transport and electron transfer for cathodic reactions in Li-O₂ batteries could be decoupled by a double-cathode structure that efficiently enables stable electron transfer between the cathode and Li₂O₂/O₂. This resolves various side reactions and slow Li₂O₂ reaction kinetics issues in conventional Li-O₂ batteries, leading to stable operation of the cell for nearly 2 months at a capacity of 0.2 and 5 mAh cm⁻², with more than 4- and 10-fold increases in cycle life when compared with single-cathode batteries. These remarkable improvements in the cyclic stability of Li-O₂ batteries with double cathodes provide an interesting concept for improving the operational stability of other metal-rechargeable batteries with conversion-type chemistry.

Wavelet-Based Texture Reformation Network for Image Super-Resolution.

Most reference-based image super-resolution (RefSR) methods directly leverage the raw features extracted from a pretrained VGG encoder to transfer the matched texture information from a reference image to a low-resolution image. We argue that simply operating on these raw features neglects the influence of irrelevant and redundant information and the importance of abundant high-frequency representations, leading to undesirable texture matching and transfer results. Taking the advantages of wavelet transformation, which represents the contextual and textural information of features at different scales, we propose a Wavelet-based Texture Reformation Network (WTRN) for RefSR. We first decompose the extracted texture features into low-frequency and high-frequency sub-bands and conduct feature matching on the low-frequency component. Based on the correlation map obtained from the feature matching process, we then separately swap and transfer wavelet-domain features at different stages of the network. Furthermore, a wavelet-based texture adversarial loss is proposed to make the network generate more visually plausible textures. Experiments on four benchmark datasets demonstrate that our proposed method outperforms previous RefSR methods both quantitatively and qualitatively. The source code is available at https://github.com/zskuang58/WTRN-TIP.

Maskin meets Abreu and Matsushima

The theory of full implementation has been criticized for using integer/modulo games, which admit no equilibrium (Jackson (1992)). To address the critique, we revisit the classical Nash implementation problem due to Maskin (1977, 1999) but allow for the use of lotteries and monetary transfers as in Abreu and Matsushima (1992, 1994). We unify the two well‐established but somewhat orthogonal approaches in full implementation theory. We show that Maskin monotonicity is a necessary and sufficient condition for (exact) mixed‐strategy Nash implementation by a finite mechanism. In contrast to previous papers, our approach possesses the following features: finite mechanisms (with no integer or modulo game) are used; mixed strategies are handled explicitly; neither undesirable outcomes nor transfers occur in equilibrium; the size of transfers can be made arbitrarily small; and our mechanism is robust to information perturbations.

High Triplet Energy Level Molecule Enables Highly Efficient Sky-Blue Perovskite Light-Emitting Diodes.

The role of triplet states in the interfacial energy transfer in perovskite light-emitting diodes (PeLEDs) has so far not been clarified because of the complex exciton recombination and decay dynamics. This work aims to study this issue and accordingly proposes a novel interfacial-engineering strategy for efficient sky-blue PeLEDs. To this end, bis[2-(diphenylphosphino)phenyl]ether oxide with a high triplet energy level is introduced into sky-blue PeLEDs. It effectively reduces undesirable exciton transfer from the perovskite emission layer to the electron-transport layer, largely suppresses exciton quenching at the interface, and simultaneously passivates defects at the perovskite surfaces. As a result of the multichannel energy-loss reduction, sky-blue PeLED that emits at 488 nm is achieved with a peak external quantum efficiency of 10.17% and a maximum brightness of 6728.41 cd m-2. This work thus provides indirect evidence for the triplet mechanism of blue emission of mixed-halide perovskites and sheds new light on a promising way of boosting the performance of blue PeLEDs.

Droplet Nucleation and Growth in the Presence of Noncondensable Gas: A Molecular Dynamics Study.

The presence of noncondensable gas (NCG) followed by undesirable heat transfer deterioration cannot be avoided in some situations. In this work, droplet nucleation and growth for the Ar-Ne mixed system are investigated using molecular dynamics simulation. Different droplet state transition modes corresponding to the subcooling degree or NCG content are obtained. The interaction between NCG and a droplet caused by gas enrichment near the solid surface is considered to explain the droplet wetting state during the condensation process. Finally, the disappearance mechanism of the flooding mode on the nanostructured surface under a large amount of NCG is clarified from the nanoscale, which could encourage a clear understanding of the NCG effect on dropwise condensation heat transfer on nanostructured superhydrophobic surfaces.

What drives Chinese overseas M&amp;A investment? Evidence from micro data

AbstractIn recent years Chinese foreign acquisitions have increased significantly. In Europe and the United States, these investments are often criticized. Critics argue that Chinese investors outbid competitors with help from their government, that the acquisitions lead to undesirable technology transfer, or that they may have negative consequences for the employees of the target firm. We use a large deal‐level dataset on cross‐border acquisitions to investigate whether Chinese foreign acquisitions differ from cross‐border investment coming from other countries. We find that relative to non‐Chinese investors, Chinese acquirers indeed appear to be different in some dimensions. They focus on targets with higher debt levels and lower profitability. At the same time, they do not seem to pay more for targets with given characteristics, questioning the view that they are subsidized to outbid other investors. Policy initiatives like the Belt and Road Initiative and Made in China 2025 influence state‐owned but not private Chinese investors, suggesting that geopolitical or technology interests play a role. In the years after the takeover, target companies acquired by Chinese investors exhibit lower growth in capital productivity but a higher growth of employee compensation.

Retracted] Applications of Wireless Communication in a New Dual Branch CTS Charge Pump Based on Employing Clock Matched Technology

With the increase in communication requirements, new communication technologies and implementation methods have developed rapidly. The rise of emerging markets such as the Internet of Things, smart homes, smart cities, and wearables has promoted the development of wireless communication integrated circuits in the direction of monolithic, low energy consumption, and high energy efficiency. This paper proposes a new dual branch charge pump based on CTS charge pump with enhanced current drive capability and undesired charge transfer completely eliminated. Clock matched technology is proposed to completely eliminate undesired charge transfer caused by delay turn on and off of the auxiliary transistors in the traditional CTS charge pump. The current drive capability is enhanced by employing NMOS transistors with 2Vdd gate drive voltage, while traditional dual branch CTS charge pumps are based on PMOS with 1Vdd gate drive voltage. The output voltage ripple is also reduced resulting from a dual branch structure. Simulation results of output voltage gain and power efficiency for the proposed charge pump and other traditional charge pumps are provided. Comparisons are made to show the improvement of the proposed charge pump compared with other traditional charge pumps.

Optimising Window Design on Residential Building Facades by Considering Heat Transfer and Natural Lighting in Nontropical Regions of Australia

Windows account for a significant proportion of the total energy lost in buildings. The interaction of window type, Window-to-Wall Ratio (WWR) scheduled and window placement height influence natural lighting and heat transfer through windows. This is a pressing issue for nontropical regions considering their high emissions and distinct climatic characteristics. A limitation exists in the adoption of common simulation-based optimisation approaches in the literature, which are hardly accessible to practitioners. This article develops a numerical-based window design optimisation model using a common Building Information Modelling (BIM) platform adopted throughout the industry, focusing on nontropical regions of Australia. Three objective functions are proposed; the first objective is to maximise the available daylight, and the other two emphasize undesirable heat transfer through windows in summer and winter. The developed model is tested on a case study located in Sydney, Australia, and a set of Pareto-optimum solutions is obtained. Through the use of the proposed model, energy savings of up to 8.57% are achieved.

Promoting effect of copper oxide on CsX zeolite catalyst for side-chain alkylation of toluene with methanol

Cesium exchanged X zeolites (CsX) have been widely used as the catalyst for toluene side-chain alkylation with methanol to produce styrene. In this work, copper oxide was recognized as an efficient promoter to improve the performance of CsX catalyst in both the reactivity and styrene selectivity. Based on systematic characterization of CuO modified CsX samples and further analysis of their catalytic performance, the promoting effect of CuO additive was explored. On one hand, the introduced Cu species promoted the dehydrogenation of methanol to formaldehyde, which acted as real alkylating agent and enhanced toluene conversion. On the other hand, the catalyst acid-base property was sensitively modulated, and thereby the undesired transfer hydrogenation of styrene to ethylbenzene was suppressed. Furthermore, the universality of CuO promoter was proved by loading on some well-known catalysts (Cs2O/CsX, B2O3/CsX and ZnO/CsX), and the effect of reaction condition was also studied with the most efficient CuO–B2O3/CsX catalyst.

A new steric tetra-imidazole for facile synthesis of high loading atomically dispersed FeN4 electrocatalysts

Abstract Atomically dispersed FeN4 rich carbon-based electrocatalysts obtained by pyrolysis of Zn-based metal-organic frameworks (mainly Fe modified ZIF-8) exhibits remarkable catalytic performance for oxygen reduction reaction (ORR). However, the independence of each ZIF-8 particle with rhomb dodecahedral results in a physical stack and undesirable charge transfer path and subsequently induce the iron buried in the carbon matrix after the pyrolysis process, which further impedes the high loading of atomic iron (usually less than 1 wt%). Herein, we newly designed a novel steric tetra-imidazole structure to anchor iron in a cross way. This strategy achieves the synthesis of atomically dispersed FeN4 rich carbon-based electrocatalyst in one-step approach without any pretreatment and/or further acid leaching. Unlike the traditional imidazole in ZIF-8, the novel steric tetra-imidazole structure exhibits a benzene ring located in the center of each four imidazole groups acting as sharing side-chain substitution, which can control the distance of each metal rivet center and impede the aggregation of iron effectively. The obtained catalyst, named as TimB-Fe5-C, exhibits high atomic iron loading content up to 2.58 wt% and exhibits efficient ORR electrocatalytic performance in both alkaline and acid medium. Significantly, this new steric tetra-imidazole endows one-step facile synthesis of atomically dispersed electrocatalysts with high loading and to avoid unpredictable changes of structure brought by tedious pre-treatment as well as post-treatment.

Improved two-phase flow boiling in a minichannel heat sink for thermal management of information and communication technology (ICT) equipment

Thermal management systems play a significant role in dissipating heat and guaranteeing the safety of facilities. For information and communication technology (ICT) systems, a highly reliable operation depends on accurate thermal control, including the maximum temperature attained and the uniformity of temperature of the semiconductor devices. In the literature, two-phase flow boiling devices have been proposed as an efficient solution for addressing this concern; however, the application of such devices is still fraught with serious challenges owing to the unstable flow boiling. This study aims at solving the problem of undesired heat transfer deterioration triggered by two-phase flow instability in ICT systems. Based on our previous proposed radial expanding minichannel heat sink (REMHS), we tested the effects of a cut-off structure and a gap structure on further stabilizing the flow boiling and enhancing heat transfer performance. The cut-off structure is employed in the flow direction to relieve the rapid expansion of vapor slugs in the minichannels. This elevated the heat transfer coefficient of the REMHS by nearly two-fold under high heat flux conditions and effectively eliminated the local hotspot on the heat sink. The overheating at the downstream of the REMHS, in terms of temperature, decreased by 55% from 29 to 13 K at a heat flux of 220 kW/m2. Moreover, a better wall temperature uniformity was obtained. The gap structure was found effective in liquid–vapor separation that maintains the temperature fluctuations below 0.6 K. By suppressing the detrimental reversal flow with the two proposed techniques, the REMHS achieved a high flow boiling heat transfer capability over a wide range of operating conditions and met the requirement of the ICT equipment thermal management system.

3D superhydrophilic polypyrrole nanofiber mat for highly efficient adsorption of anionic azo dyes

The demand for cost-effective, easy-handling, and recyclable adsorbents with high performance for removal of organic dyes is gaining prominence. Although polypyrrole (PPy) has proven to be promising for adsorption of anionic azo dyes (AADs), the use of PPy-based particles and fibers still faces limitations such as challenging separation and undesirable mass transfer. In this work, a superhydrophilic polypyrrole nanofiber mat (PPy NFM) with a 3D fluffy porous structure was developed via in situ polymerization of pyrrole monomers with electrospun PAN@PVP NFM as the substrate and followed by freeze-drying. The 3D PPy NFM exhibited a fast adsorption rate (within 3 h) and high adsorption capacity (up to 234.62 mg g−1) towards AADs, remarkably superior to those of 2D lamellar PPy NFM. After five times of reuse, the reduction of adsorption capacities for AADs was less than 10%. Another striking advantage of the 3D PPy NFM lies in the integration of dispersibility and integrity, making it easy to use and recycle without centrifugation or filtration. Moreover, the adsorption behaviors of three dye models, Metanil Yellow (MY), Acid Orange 7 (AO7), and Acid Yellow 9 (AY9), were thoroughly discussed, suggesting that the adsorption of AADs by the PPy NFM involves multiple mechanisms, including electrostatic attraction, π–π interaction and hydrogen bonding, thus ensuring high adsorption efficiency. These attractive characteristics make 3D PPy NFM be a potential eco-friendly adsorbent in dye wastewater treatment.

N-Heterocyclic carbene/Lewis acid-mediated ring-opening polymerization of propylene oxide. Part 2: Toward dihydroxytelechelic polyethers using triethylborane

Propylene oxide (PO) is polymerized by metal-free ring-opening polymerization (ROP) at 25 °C using N-heterocyclic carbenes (NHCs) and triethylborane (Et3B) as a bicomponent catalytic system. Poly(propylene oxide)s with predictable molar mass up to 60 000 g·mol−1 and low dispersity (Ð < 1.10) were obtained without the occurrence of undesirable transfer reaction to the monomer. In presence of an alcohol as the initiator, the ROP of PO follows an anionic mechanism assisted by monomer activation improving the efficiency of NHCs for the polymerization of substituted epoxides. Et3B is involved both in the formation of a complexed active center and in the activation of PO. Interestingly, dihydroxytelechelic PPOs can be readily synthesized not only using 1,4-benzenedimethanol but also water, both serving as difunctional initiators. Block copolyethers are also prepared by PPO chain extension experiments. All (co)polyethers have been thoroughly characterized by 1H NMR spectroscopy, SEC and MALDI-TOF mass spectrometry as means to elucidate the reaction mechanisms involved in this chemistry.

A 3D inlet distributor employing copper foam for liquid replenishment and heat transfer enhancement in microchannel heat sinks

The application of two-phase flow boiling to microchannel heat sinks has attracted increasing attention owing to the compact design and high efficiency of dissipating heat. However, undesirable heat transfer deterioration and premature critical heat flux are commonly encountered in real-life applications of two-phase flow cooling devices. One significant challenge in utilizing two-phase flow boiling in microchannels lies in preventing the thin liquid film and in-time liquid replenishment from being interrupted by the rapid bubble elongation and chaotic vapor-liquid interface in the channel. In the present work, a 3D inlet distributor employing copper foam is proposed as an extra liquid feeding path to facilitate continuous liquid wetting of the boiling surface and improve the heat transfer performance. A physical heat transfer model accounting for the differences in microchannel void fraction and liquid film thickness caused by the copper foam layer (CFL) has been proposed to describe the working mechanism. The validity of the proposed 3D inlet distributor in heat transfer enhancement was verified using a series of flow boiling tests, employing deionized water as the working fluid. It was found that the local overheating of the microchannel heat sink was demonstrably reduced for all the heat flux values (q) in the tests after adopting the CFL, with a maximum reduction of 14 K at q = 397.6 kW/m2, where local dry-out was successfully inhibited. The heat transfer coefficient of the microchannel heat sink with the CFL was improved by approximately 1.7 times compared to the case without the CFL and could be maintained at 41 kW/m2K during elongated bubble flow and annular flow patterns. In addition, the proposed distributor was capable to resist gravity and long-term severe boiling, thus achieving superior and reliable performance under various orientations as well as during long operating hours.

Carbon Nanotube Film Electrodes with Acrylic Additives: Blocking Electrochemical Charge Transfer Reactions.

Carbon nanotubes (CNTs) processed into conductive films by liquid phase deposition technologies reveal increasing interest as electrode components in electrochemical device platforms for sensing and energy storage applications. In this work we show that the addition of acrylic latex to water-based CNT inks not only favors the fabrication of stable and robust flexible electrodes on plastic substrates but, moreover, sensitively enables the control of their electrical and electrochemical transport properties. Importantly, within a given concentration range, the acrylic additive in the films, being used as working electrodes, effectively blocks undesired faradaic transfer reactions across the electrode–electrolyte interface while maintaining their capacitance response as probed in a three-electrode electrochemical device configuration. Our results suggest a valuable strategy to enhance the chemical stability of CNT film electrodes and to suppress non-specific parasitic electrochemical reactions of relevance to electroanalytical and energy storage applications.

A low-voltage with high pumping efficiency charge pump for flash memory

This paper proposed a high efficiency of power conversion and high pumping gain charge pump applied to the field of low power consumption like flash memory. The threshold voltage drop, body effect and the undesired charge transfer are three significant factors limiting the pumping gain and power conversion efficiency. In order to solve the threshold voltage drop and body effect, the charge transfer switches (CTS) are utilized in the proposed charge pump. What’s more, an optimized substrate control strategy and body-source diode are applied to eliminate undesired charge transfer for improving power efficiency. And a complementary branch scheme is employed to reduce the output voltage ripple. The proposed charge pump is implemented in SMIC 0.18 um standard technology and the simulation results indicate better performance and high efficiency of power conversion. The proposed charge pump satisfies the relevant specifications of the charge pump applied to flash memory.

A Low Input Voltage Charge Pump for Energy Harvesting

This paper proposes a low input voltage charge pump using 0.18um CMOS process for energy harvesting. There are two main sections in the charge pump system: Low Voltage Charge Pump (LVCP) and High Voltage Charge Pump (HVCP). In the LVCP, a negative charge pump is utilized to improve the efficiency at low input voltage, Dynamic Body Bias (DBB) and switch-conductance enhancement techniques are applied to a unit stage of the two-stage charge pump. In the HVCP, the charge pump circuit utilizes charger transfer switches (CTS) with a complementary banch scheme to significantly reduce undesired charge transfer, and an optimized gate control strategy is applied to further decrease the power loss caused by undesired charge transfer. The simulation result demonstrates that the proposed circuit can achieve 97% voltage conversion and drive 800uA load current at 0.6V input voltage. In the region of 0.4V to 0.6V input voltage, the circuit performs well with the load resistance of 10K ohms.

Bridge engineering in photocatalysis and photoelectrocatalysis.

Solar driven photocatalysis and photoelectrocatalysis have emerged as promising strategies for clean, low-cost, and environmental-friendly production of renewable energy and removal of pollutants. There are three crucial steps for the photocatalytic and photoelectrochemical (PEC) processes: light absorption, charge separation and transportation, and surface catalytic reactions. While significant achievement has been made in developing multiple-component photocatalysts to optimize the three steps for improved solar-to-chemical energy conversion efficiency, it remains challenging when weak interfacial contact between components/particles hinders charge transfer, restricts electron-hole separation and lowers the structural stability of catalysts. Moreover, owing to the mismatch of energy bands, an undesirable charge transfer direction leads to an adverse consequence. To tackle these challenges, bridges are implemented to smoothen the interfacial charge transfer, improve the stability of catalysts, mediate the charge transfer directions and improve the photocatalytic/PEC performance. In this review, we present the advances in bridge engineering in photocatalytic/PEC systems. Starting with the definition and classifications of bridges, we summarize the architectures of the reported bridged photocatalysts. Then we systematically discuss the insight into the roles and fundamental mechanisms of bridges in various photocatalytic/PEC systems and their contributions to activity enhancement in various reactions. Finally, the challenges and perspectives of bridged photocatalysts are featured.

Transfers to lunar libration point orbits

In this paper, two-impulse transfers from low Earth orbit (LEO) to libration point orbits (LPOs) near the Moon are investigated. The transfer orbit is separated into two portions: trans-lunar and manifold segments. Based on locations of apogees of transfers, transfer orbits are classified into short and long transfers. For short transfers with duration shorter than 50 days, trans-lunar segments are analyzed preliminarily in the two-body model. Using the optimal manifold injection points of the preliminary analysis as initial guesses, short transfers are constructed and compared in the Earth-Moon circular restricted three-body problem. Since undesirable short transfers with large fuel cost are excluded by the preliminary analysis, our results are more selective than previous researches. Using lunar flyby transfers from LEO to low Moon orbits as initial guesses, long transfers are designed and discussed in the Sun-Earth-Moon restricted four-body problem. Since lunar flyby is necessary for Pareto-efficient solutions, our design method of long transfers is more targeted and efficient compared with the previous optimization of low-energy transfers. Finally, the obtained short and long transfers are extended to the ephemeris model.

Impact of shadow distribution on optimizing insolation exposure of roofs according to harness or transfer of solar energy in Sulaimani city, Iraq

Shadow area distribution of vertical elements mounted on flat roofs was studied regarding its impact on opportunities for harnessing solar energy and its positive effect on obstructing undesirable heat transfer. Various cases were assumed for the position of a penthouse on flat roofs of dwelling units. In each case the spatial distribution of the shadow was studied on the host roof and its neighbors. The general constant ratio between the average annual shadow and lateral area of a rectangular shape was found to be 0.88. The north direction and the back penthouse position receive the highest quantity of annual shadow on the host’s roof (2.85 times its roof area). The left corner roofs offer better opportunities compared to the middle and right corner roofs for collecting solar energy, on average 1.5 and 1.3 times, respectively. Left corner roofs with front penthouse position receive the highest amount of insolation energy per unit area, which makes it the favorable position for harnessing solar energy. The highest positive obstructed insolation is in 0° orientations and 180° penthouse position by 413 kWh/m2/year. Generally, the back penthouse position performs better than the center and front positions in terms of obstructing negative heat transfer.