Liquidity Provision Research Articles

Pool boiling performance of TiO2 superhydrophilic and Teflon superhydrophobic surfaces on evenly deposited copper frustums

The miniaturization of electronic devices with ever-increasing functionalities inevitably results in greater thermal load on the devices. Hence, pool boiling, which utilizes the powerful latent heat of vaporization, is introduced as an effective method to manage severe thermal loads on miniaturized electronics. Hydrophobic surfaces tend to augment sufficient nucleation sites via roughening or low surface energy, while hydrophilic surfaces are prone to ample liquid supply, thus facilitating rapid bubble release and preventing surface dry-out. Herein, we compared the heat removal performance of TiO2-coated superhydrophilic and Teflon-coated superhydrophobic surfaces fabricated by aerosol deposition and supersonic spraying, respectively. TiO2 and Teflon particles were deposited on evenly patterned frustums. The resolution of the frustum is categorized as no-frustum, coarse, medium, or fine. We found that the surface wettability had little effect on the critical heat flux (CHF) for the no-frustum and fine cases. However, the CHF and effective heat transfer coefficient (heff) of the superhydrophilic surface increased considerably in the medium case. For the superhydrophobic surface, the presence of frustum deteriorated the pool boiling performance. Frustum texturing enhanced the pool boiling performance by increasing the number of nucleation sites and pathways of fresh liquid supply for the bare and superhydrophilic surfaces, but not for the superhydrophobic surface.

Investigation of quench flow boiling heat transfer correlations for liquid oxygen feed line chill-down with outlet contraction

Cryogenic feed lines used for ground-based liquid transfer, thermal management in space flight, as well as the one with an injector at the outlet used for supplying propellants to the cryogenic engine combustion chamber, undergo an initial transient cool-down operation before vapor free liquid supply can be established through them. Accurate prediction of the thermal and hydraulic transients during this period has critical importance in the safe operation and efficient utilization of the cryogen. In the present work, a one-dimensional non-homogeneous two-phase model is used for simulating the chill-down operation in feed lines with and without outlet contraction. For transport feed lines without outlet constriction, the obtained transient wall temperature profiles indicate good prediction when the heat transfer correlations proposed based on recent chill-down experiments are employed as constitutive relations. Subsequently, the numerical model is applied for predicting the wall temperature transients during outlet contracted LOX feed line chill-down. It was noted that built-in heat transfer correlations in thermal–hydraulic code SINDA/FLUINT need revision, especially for rewetting point and heat transfer correlation during post rewetting regimes, for accurate thermal transient predictions during end constrained feed line chill-down. Hence, recent chill-down correlations reported in the literature and the correlations employed in previous chill-down numerical models are tested for their applicability. The recent cryogenic chill-down correlations reported in the literature performed well when applied within the correlation range. However, these correlations over predict the heat transfer at a very high mass flux (order of 3412 kg/m2 s). Hence, modified correlations are proposed for film and nucleate boiling heat transfer coefficients and rewetting temperature.

Fault Diagnosis Algorithm of Beam Pumping Unit Based on Transfer Learning and DenseNet Model

The difficulty of collecting fault data samples is one of the application problems of the deep learning method in fault diagnosis of mechanical production; the second is that when the depth of the learning network increases, the network accuracy is saturated or even decreased. Therefore, based on the deep learning algorithm and the DenseNet model, this paper establishes a fault diagnosis model for the beam pumping unit through the transfer learning method. The model uses the global pooling layer as the classifier. The model is used to classify and test various working conditions such as wax deposition, pump leakage, insufficient liquid supply, and pump leakage in oil wells. The results show that the model can obtain a classification model with high accuracy by learning a limited number of sample data; in the case of uneven data samples, the model can also basically complete the task classification task accurately. Through the evaluation of the test set, the model has an average accuracy of more than 95% in identifying various working conditions.

FX swaps, shadow banks and the global dollar footprint

The era of dollar-based financial globalisation has seen a steady rise in the use of foreign exchange (FX) swaps. We provide a macrofinancial political economy perspective on the geography of FX swaps, and the spatial effects of central bank policies aimed at taming instabilities associated with the uneven geography of the dollar. First, we analyse the mechanisms and potential sources of instability involved in accessing dollars using FX swaps and repurchase agreement (repo) contracts, respectively, in both private and public (central bank) use. Second, we show that the distribution of currencies and institutions involved in trading swaps is skewed, reflecting both the dominance of the dollar as international financing currency and the uneven international distribution of dollar-denominated assets and liabilities. We document the changing composition of dollar swap users on both the long-dollar and short-dollar side and identify potential sources of macrofinancial vulnerability for dollar lenders and borrowers. The Fed's approach to global liquidity provision via both swaps and repos constitutes a spatially variegated strategy to preserve the hegemony of the US dollar. Despite its partial success in reducing instability due to cross-border financial imbalances, the Fed's uneven and hierarchical lender of last resort approach cannot sufficiently stabilise global finance to underpin a new era of macrofinancial stability.

“Where’s my swap line?”

Abstract The past two decades have seen the construction of a tiered system of international liquidity provision, the first tier including those whose credit is sufficient for a swap line with the Fed, the second tier including those who can offer acceptable collateral to the Fed, and the third tier including everyone else. It is a global dollar system, with the Fed operating de facto as the global central bank providing international lender of last resort support to the system. It is a system created not so much by conscious design, but rather as a pragmatic response to crisis, bit by bit over time.

When Bigger is Better: The Impact of a Tiny Tick Size on Undercutting Behavior

AbstractEconomically insignificant tick sizes encourage undercutting behavior, thus harming market quality. Theoretical work shows that increasing tick sizes in unconstrained markets reduces undercutting and improves market quality. Equity market pricing grids are generally too coarse to test this prediction. We examine a cryptocurrency market with infinitesimal tick sizes where undercutting limit orders acquire price priority without meaningful economic cost. We show that increasing tick sizes reduces undercutting behavior, increases liquidity provision and quoted depth, and reduces transaction costs for institutional and retail-sized trades while decreasing short-term volatility. Tiny tick sizes are suboptimal, supporting increased minimum trading increments in tick-unconstrained markets.

Heat transfer enhancement of spray cooling by copper micromesh surface

Spray cooling has become one of the most promising heat dissipation technologies for thermal management of super high heat flux. The traditional strategies to enhance spray cooling have mainly strengthened the forced convection at high spray flow rate, or extended the triple line area for evaporation by micro/nano structure, which is challenging in promoting heat transfer efficiency. In this work, multi-layer copper micromesh is applied to increase the heat transfer proportion of liquid film boiling in spray cooling, which improves onset of nucleate boiling (ONB), and enhances the critical heat flux (CHF) and heat transfer coefficient (HTC) simultaneously. Synergistic effects of micromesh structures (including thickness and spacing width) and spray flow rate on liquid supply and bubble escape are demonstrated: high micromesh thickness, small wire spacing width, and large spray flow rate increasing liquid supply but impeding bubble escape. It is shown that the surface temperature at ONB on multi-layer micromesh has decreased by 16 °C approximately, and #100 4-layer micromesh sample exhibits the best heat transfer performance at 1.14 ml/s with CHF of 605.2 W/cm2 and maximum HTC of 71.45 kW/(m2·K), which is enhanced by 127.3% and 175.7% compared with flat surface, respectively.

A Two-Dimensional Numerical Analysis of Transient Falling-Film Hydrodynamics on Horizontal Tubes

Falling-film hydrodynamics and heat transfer, a cutting-edge technology, has been widely used in a variety of industrial applications, including desalination and refrigeration. In this study, a two-dimensional and two-phase model was developed to examine the microscopic flow mechanism and transient flow characteristics. Film thickness varies with sprinkle density in the impingement, propagation, and accumulation zones, with the thinnest film appearing between 90° and 140°. In both the unsteady and steady cases, the film thickness over the stabilizing tube is nearly the same. Due to the acquired momentum of the liquid film, the propagation time for the test tube was also shorter than that of the stabilizing tube. Low sprinkle density results in dry regions; high sprinkle density results in mal-distribution, the formation of recirculation zones beneath the tubes, air cavities in the flow field, wavy disturbances in the liquid profile, and fluid waste. Furthermore, as the liquid sprinkle density increases, the developed recirculation zones and air cavities beneath the tubes expand and become modified. A sprinkle density can be set just above the minimum value to achieve steady-state film thickness. The findings can be used to improve flow characteristics and avoid over commitment and insufficient liquid supply.

The Impact of High-Frequency Trading on Modern Securities Markets

High-frequency traders account for a significant part of overall price formation and liquidity provision in modern securities markets. In order to react within microseconds, high-frequency traders depend on specialized low latency infrastructure and fast connections to exchanges, which require significant IT investments. The paper investigates a technical failure of this infrastructure at a major exchange that prevents high-frequency traders from trading at low latency. This event provides a unique opportunity to analyze the impact of high-frequency trading on securities markets. The analysis clearly shows that although the impact on trading volume and the number of trades is marginal, the effects on liquidity and to a lesser extent on price volatility are substantial when high-frequency trading is interrupted. Thus, investments in high-frequency trading technology provide positive economic spillovers to the overall market since they reduce transaction costs not only for those who invest in this technology but for all market participants by enhancing the quality of securities markets.

Study on the effect of nanoparticles combined with silicone surfactant and cationic surfactant on foam and fire extinguishing performance.

Aqueous film-forming foam (AFFF) in firefighting foam can effectively extinguish oil fire. However, AFFF will be phased out due to the presence of persistent organic pollutants such as perfluorooctane sulfonates. It is necessary to explore environment-friendly foam extinguishing agent. Silicone surfactant is a kind of environmentally friendly surfactants with high surface activity, which can be used as a substitute for fluorocarbon surfactant. In this study, silicone surfactant and cationic surfactant were combined to adsorb nanosilica particles to form a multiphase system. The foaming property and foam stability of the multiphase system were tested by stirring method. The foam suppression effect on fuel vapor, fire extinguishing, and burn-back performance was tested by self-designed foam suppression device and foam generating device of porous glass with recyclable liquid supply. The experimental results show that foam stability is enhanced and the foaming property is slightly decreased after the addition of nanoparticles. When the component of three-phase foam reaches the optimum, its suppression effect on fuel vapor is better than that of two-phase foam. The results of fire extinguishing and burn-back performance test showed that the fire extinguishing effect of three-phase foam was slightly worse than that of AFFF, but it has extremely strong burn-back performance.

Liquidity Provision with Adverse Selection and Inventory Costs

We study one-shot Nash competition between an arbitrary number of identical dealers that compete for the order flow of a client. The client trades either because of proprietary information, exposure to idiosyncratic risk, or a mix of both trading motives. When quoting their price schedules, the dealers do not know the client’s type but only its distribution, and in turn choose their price quotes to mitigate between adverse selection and inventory costs. Under essentially minimal conditions, we show that a unique symmetric Nash equilibrium exists and can be characterized by the solution of a nonlinear ordinary differential equation.

Internal risk limits of dealers and corporate bond market making

Using novel supervisory data reported in the Volcker metrics, we examine how the internal risk limits of bank-affiliated corporate bond dealers evolved from 2017 to 2020 as indication of capacity constraints on their market making activity. We document that dealers’ internal risk limits came closer to binding during the March 2020 market turmoil. Although dealers eased their limits to accommodate increased liquidity demand, limit adjustments were not enough to offset the increase in risk exposures. We find limit tightness is negatively associated with subsequent inventory growth at dealers’ bond trading desks, especially during the COVID-19 crisis or on days with limit changes. Overall, our results indicate the importance of internal risk limits in driving dealers’ liquidity provision in time of stress.

A Review of China's Financial Markets

The fast growth of China's economy has brought it not only to the center of the global economy but also to a transition point in its growth model, a transition from scale to efficiency, speed to sustainability, input driven to innovation led. How its financial markets can drive this new growth model and facilitate the transition are pressing challenges, for China and for the world. We provide a comprehensive review of China's financial markets, including government bonds, corporate/credit bonds, stocks, asset-backed securities, financial derivatives, investment management, and currency, focusing on their growth paths, distinct characteristics, and unique opportunities. Despite fast expansion at times, their development is often lagging behind market needs, uneven over time, and unbalanced across markets. This developmental pattern is driven mostly by the government's immediate policy objectives rather than by the markets' ultimate efficiency in serving their key functions, including liquidity provision, price discovery, and risk allocation.

Study on Conduction Cooling of Superconducting Magnets for the ILC Main Linac

In the main linac of the International Linear Collider (ILC), superconducting magnets for beam focusing and steering will be located periodically in superconducting RF (SRF) cavity string for beam acceleration in common cryomodules. A concept of conduction cooling of the combined-functioned, splittable superconducting magnets has been proposed and investigated to adapt much different features and to meet different requirements for the superconducting magnet and SRF cavity in fabrication, assembly, and operation. It is required to integrate the superconducting magnet after the SRF cavity string assembly which completed under an ultra-clean environment. The magnet must be conductively cooled down through thermal links to a liquid helium supply pipe. According to this concept, a model magnet development was carried out in cooperation with Fermilab and KEK, and has been demonstrated in KEK superconducting RF test facility (STF). In addition, an important issue has been recently identified. High gradient SRF cavities naturally emit field emission electron flux from the inner surface, so-called dark current. It may pass through the subsequent SRF cavity string and penetrate into the superconducting magnets placed downstream. It may heat up the superconducting coils, and may cause a quench. Therefore, further study on reliable conduction cooling and to secure the superconducting magnet operation with a keeping sufficient safety margin is quite essential. In this paper, we report the installation, the improvement achieved in STF, and the R&D progress in the study on the conduction cooling of the superconducting magnet for the ILC main linac.

Visualization study on preferential flow in highly saturated and super hydrophilic porous media by combining dye tracking and infrared imaging

• New method to track finger flow in highly saturated superhydrophilic porous media. • Preferential flow recurrence was observed at high saturation. • The preferential flow was found to impair desalination efficiency. • The temperature distribution was controlled by preferential flow. Air-gap diffusion distillation (AGDD) is a practical desalination technique. The highly saturated super hydrophilic porous medium as its evaporation surface has a decisive influence on the desalination efficiency of AGDD. In experiments, we found preferential flow in porous media. However, the preferential flow in highly saturated super hydrophilic porous media has not been studied, and the effect of preferential paths on evaporation from porous media surfaces remains poorly understood. The method of combining dye tracking and infrared imaging was used to visualize the process of thermal seepage in highly saturated super hydrophilic porous media. Under the condition of uniform and continuous liquid supply on the upper surface, the preferential flow characteristics of hot stream seepage in porous media are tracked; Point source infiltration experiments were carried out at room temperature to compare the difference between preferential flow in super hydrophilic porous media and general soil (sand). The experimental results of thermal seepage showed that the preferential flow greatly influences the uneven temperature distribution of the porous media, which directly impairs the desalination efficiency of AGDD. According to the coefficient of variation (CV), the preferential flow development process can be divided into three stages: stable development, exponential development, and high-speed growth. As the seepage flow is stabilized, the influence of preferential flow on the flow field and temperature field still exists and is affected by these three stages. Preferential flow characteristics were also captured in the saturated capillary rise zone at the bottom of the porous medium (below the phreatic level). The point source infiltration experiment found that the preferential flow in superhydrophilic porous medium will reappear at high saturation, which is completely different from the soil (sand) studied by previous studies. In addition, the effects of inlet temperature, flow rate, thickness, and hydrophilic, hygroscopicity on preferential flow were discussed. Increasing the flow rate and inlet temperature and reducing the thickness of the porous media can weaken the influence of preferential flow on the temperature field. But increasing the temperature only superficially weakens the preferential flow. Increasing hydrophilicity and hygroscopicity can also reduce the preferential flow.

Cross-border interbank liquidity, crises, and monetary policy

We analyze how the Lehman and sovereign crises affect cross-border interbank liquidity, exploiting euro-area proprietary interbank data, crisis and monetary shocks, and loan terms to the same borrower during the same day by domestic versus foreign lenders. Crisis shocks reduce the supply of cross-border liquidity, with stronger volume than pricing effects. On the extensive margin, results suggest that the cross-border credit crunch is independent of borrower quality, while—on the intensive margin—riskier borrower banks suffer more. Moreover, the cross-border liquidity crunch is substantially stronger for term loans, and weaker for foreign lender banks that have a subsidiary in the same country than the borrower. Finally, nonstandard monetary policy improves interbank liquidity, but without fostering strong re-integration of cross-border interbank markets.

A taxonomy of individual liquidity provision: Evidence from the Taiwan stock exchange

Using trade-level data from the Taiwan Stock Exchange, we document an asymmetric pattern of liquidity provision by individual investors who serve as de facto market makers. Specifically, on average, individual investors provide more liquidity during market declines. We further investigate the impact of asymmetric individual liquidity provision on market efficiency. Despite being uninformed, individual investors’ liquidity provision ameliorates market efficiency more during market declines. Our results suggest that individual investors provide liquidity to help those with private information correct prices toward efficient prices, in turn, enhancing market efficiency.

Electrospray characteristics and cooling performance of dielectric fluid HFE-7100

Electrospray (ES) cooling is a promising route of efficient heat removal for electronic components with powerful cooling capacity, a small liquid supply, and precise temperature control. In this study, we experimentally investigated the electrohydrodynamic (EHD) disintegration and ES cooling performance of the dielectric fluid HFE-7100. The stainless-steel capillary nozzle was connected to a high voltage direct current (DC) power supply, whereas the hot copper surface was grounded. A high-speed camera was used to capture the spray morphology of the coolant. The results indicated that a small amount of ethanol significantly improved the charging performance of HFE-7100 by increasing the liquid electrical conductivity. An uncharged column liquid jet was stretched into a thin liquid film by the EHD forces, generating numerous ultrafine droplets along the lower edge. The ES cooling heat flux was increased by about 2.2 times compared with the neutral condition. In addition, the influences of the applied voltage, flow rate, spray height, liquid subcooling, and ethanol concentration on the ES cooling capacity were discussed. Finally, correlations of the ES cooling heat transfer based on the Reynolds number, Weber number, Prandtl number, electric Weber number, Jacob number, and normalized surface temperature were established.

Tick Size, Institutional Trading, and Market Making: A Study of the SEC Tick Size Pilot Program

Using the 2016 SEC Tick Size Pilot Program, we study the effects of an increase in tick size on institutional trading, market making costs, profitability, and activities. We find that increasing the tick size deters institutional trading participation, as it results in unfavorable stock characteristics, such as greater price impact and depressed share prices. In particular, we show that the implementation of the pilot program creates a substitution effect, which causes mutual funds to migrate from pilot (wider-tick) stocks to control (narrower-tick) peers. Furthermore, we document that widening the tick size increases adverse selection and inventory costs and thus reduces market making profitability, leading to lower market-making activities. Further analysis shows that these adverse effects can be attributed to the trade-at rule that prevents price-matching in non-displaying trading centers, while the quote rule that mandates a minimum quote increment of five cents enriches market makers and promotes liquidity provision. Finally, we show that our results are more pronounced for tick-constrained stocks than for unconstrained ones. Overall, the evidence contradicts the SEC’s intent to use a larger tick size to incentivize market making in small-cap stocks and attract more investors to trade these stocks, and dispraises the “one-size-fits-all” approach undertaken by regulators.

Is short-term reversal driven by liquidity provision in emerging markets? Evidence from China

Studies focusing on the U.S. stock markets argue that the short-term reversal is related to liquidity provision. We test the implications of the theory of liquidity provision to investigate the profitability of reversal trading strategies in the Chinese markets. We find highly robust and puzzling patterns that are mainly inconsistent with findings in the U.S. markets and liquidity provision. There is a momentum based on the most recent day instead of reversal, only few specific days drive the profitability of the reversal strategies, and even these profits do not depend on liquidity constraints as liquidity provision theory implies.