Strong Momentum Research Articles

A Study of Variations in Correlation Between Rotation Residual and Meridional Velocity of Sunspot Groups

We analyzed the combined 142 years sunspot-group data from Greenwich Photoheliograpic Results (GPR) and Debrecen Photoheliographic Data (DPD) and determined the yearly mean residual rotation rate and the meridional velocity of sunspot groups in different 5-degree latitude intervals. The residual rotation rate is found to be -120 m/s to 80 m/s. In a large number of solar cycles the rotation is to some extent weaker during maxima than that of during minima. There exist alternate bands of equatorward and poleward merdional motions. The equatorward motion is dominant mostly around the maxima of solar cycles with velocity 8-12 m/s, whereas the poleward motion is dominant mostly around the minima but with a relatively weak velocity, only 4-6 m/s. This analysis suggests the existence of equatorward migrating alternate bands of slower and faster than average rotation within the activity belt and no clear equatorward or poleward migrating bands of meridional motions. A statistically significant anticorrelation exists between the meridional motion and residual rotation. The corresponding linear-least-squares best-fit is found to be reasonably good (slope, -0.028 + or - 0.008, is about 3.5 times larger than its standard deviation). The significant negative value of the slope indicates the existence of a strong angular momentum transport toward equator. The slope leads sunspot number (SN) by about 4 and 9 years. The Morlet wavelet spectrum of the slope suggests the existence of approximate 11-year periodicity in the slope almost throughout the data window, but it was very weak during 1920-1940.Overall the results suggest there exits a strong relationship between the slope and amount of activity during a solar cycle. However, no relationship is found between the slope and strength of activity on a long-time scale (longer than 11-year period).

Research Networks Generated by Organizational Structures, Co-Authorships and Citations: A Case Study of German Centre for Integrative Biodiversity Research (Idiv)

Exploring whether different patterns emerge across networks generated by organizational structures, co-authorships and citations for characterizing and evaluating cooperative relationships is particularly important for transferring the research results into practice. This research-in-progress paper focuses on using the structure of scientific collaborations and mapping knowledge transfer to gain insight into the influence of collaborative research centres linked to the German Research Foundation (DFG) funding. Within the German Centre for Integrative Biodiversity Research (iDiv), the DFG sponsors research conducted across all participating universities and institutes by more than hundred research groups who bring their expertise to the manifold research fields of biodiversity. Using iDiv research from 2013-2020, we build co-authorship networks and identify the most cohesive communities in terms of collaboration and compare them with groups presented on its website. Corresponding cited and citing works are analysed by distributions to investigate disciplinary collaboration. Our findings show that the number of publications and the intensity of research collaboration have maintained a steady increase. Despite the highly cohesive cooperation structure addressed by iDiv, the internal scientific collaboration has not gained strong momentum compared with its growing trends in international collaborations. The tendency towards covering cross-disciplinary research foci is not evident.

Under-reaction in the sovereign CDS market

The sovereign CDS market has developed rapidly for two decades and currently has a gross notional amount of more than a trillion dollars. We document a strong momentum effect in this market, which cannot be explained by a large set of risk factors. These momentum returns are positively skewed and higher during recessions. Consistent with the interpretation that this momentum effect is due to investors’ initial underreaction to sovereign credit information followed by corrections, our evidence shows that the momentum returns tend to be higher during the months surrounding announcements of credit rating or outlook changes of the underlying countries.

Growing With Lady Flower Gardens: Governance in a Land-based Initiative Focused on Building Community, Well-being and Social Equity Through Food

The local food sector has been gaining strong momentum in the province of Alberta but inclusiveness, social equity, and affordability remain issues of concern. Lady Flower Gardens (LFG) is a community-based initiative that is working to address these issues. Established in 2012 on private land in the northeast edge of Edmonton, Alberta, LFG provides opportunities for marginalized and disadvantaged individuals to develop skills in growing food for their own consumption, contribute a share of the harvest to the Edmonton Food Bank, and develop relationships and build community in a healthy and safe environment. LFG collaborates with a number of social service agencies and two universities in the development of this land-based, experiential learning model. In this case study we examine LFG’s evolving governance structure, from a small informal grassroots initiative to a self-governed Part 9 non-profit company, registered with the provincial government. We gathered data from in-depth semi-structured interviews as well through site visits, participant observation and documentary research. Our analysis uses a food justice lens and the Policy Arrangement Approach as adapted by Van der Jagt et al. (2017) to examine LFG’s actors, partnerships and participation, resources, discourse, and rules. Investigating these dimensions of LFG provides insights into the complexity of factors, both internal and external, that have influenced the development and governance of this local food initiative and its ability to contribute to inclusiveness, social equity, and food justice. Our research reveals that LFG aligns strongly with FLEdGE’s good food principles of food access and ecological resilience, while also intersecting with the principle of farmer livelihoods through the creation of new training opportunities.

Stereo PIV measurements of oscillatory plasma forcing in the cross-plane of a channel flow

The present work describes an experimental investigation that applies stereo particle image velocimetry in a cross-plane of a turbulent channel flow that is additionally perturbed by spanwise oscillatory body forces, induced by a plasma actuator and designed to mimic the effect of spanwise wall oscillations. The experiment is aimed at retrieving the forcing-correlated scales and the turbulent flow stochastic fluctuations for the measured cross-plane. The first are macroscopic scales and require a larger investigation domain while the latter benefit of a higher resolution. Furthermore, the extended flow-field dynamic range posed a challenge on the experiment design, finally leading to an optimal tradeoff. The results of the unactuated flow compare well to the direct numerical simulations of Hoyas and Jimenez ́ (2008), while the actuated case demonstrates strong near-wall momentum addition and spanwise modulation of the streamwise flow component.

Energy spectra of Sub-Surface Velocity Fields Beneath Faraday Waves

Faraday waves form on the surface of a fluid which is subject to vertical forcing, and are researched in a large range of applications. Some examples are the formation of ordered wave patterns and the controlled walking or orbiting of droplets (Couder et al. (2005); Saylor and Kinard (2005)). Moreover, recent studies discovered the existence of a horizontal velocity field at the fluid surface, called Faraday flow, which was shown to exhibit an inverse energy cascade and thus properties of two-dimensional turbulence (von Kameke et al., 2011, 2013; Francois et al., 2013). Additionally, three-dimensionality effects have been part of recent investigations in quasi-2D flows (both electromagnetically-driven (Kelley and Ouellette, 2011; Martell et al., 2019) or produced by parametrically-excited waves (Francois et al., 2014; Xia and Francois, 2017)). Furthermore, the occurrence of an inverse cascade in thick layers is also subject of current studies on the coexistence of 2D and 3D turbulence (Biferale et al., 2012; Kokot et al., 2017; Biferale et al., 2017). By performing 2D PIV measurements at horizontal planes beneath the Faraday waves, we recently showed that pronounced three dimensional flows occur in the bulk, with much larger spatial and temporal scales than those on the surface (Colombi et al., 2021), when the system is not shallow in comparison to typical length scales of the surface flow (fluid thickness exceeding half the Faraday wavelength λF). This in turn reveals that an inverse energy cascade and aspects of a confined 2D turbulence can coexist with a three dimensional bulk flow. In this work, 2D PIV measurements of the velocity fields are carried out at a vertical cross-section xz-plane and at four distinct horizontal xy-planes at different depths in Faraday waves. The results reveal that small and fast vertical jets penetrate from the surface into the bulk with fast accelerating bursts and strong momentum transport in the z−direction. Furthermore, the fraction of flow kinetic energy in the vertical direction is found to peak inside a layer of approximately 10 mm (one Faraday wavelength) below the fluid surface.

Towards the Implementation of Monetary Management in Islamic Economic System Based on Recent Developments

Monetary management is an essential part of the objectives of Shari’ah under the umbrella of the preservation of wealth (Ma’al). Our primary sources: Qur’an and Sunn’ah, provide divine legislation on the prohibition of Riba to manage bases of monetary transaction. Further, the juristic tools facilitate scholars to propose solutions to meet the emerging issues on diversified aspects of society. Muslim scholars have always adapted and contributed to the Islamic finance system and regulation, theoretically and practically. In recent decades, Islamic banking and finance has seen strong momentum with double digit growth, fulfilling the monetary requirement of depositors on the liability side along with industry on the asset side. We seek to review the theoretical and empirical literature on Islamic monetary mangement. Monetary management in the Islamic economic context is still an area that needs more research. This paper examines how literature has been developed over time up until modern Islamic economic and banking practices. The findings suggest that Islamic monetary management has been gradually developed in recent years and such development is remarkable steps forward in pursuing Islamic monetary policy independently. In addition, Islamic monetary policy is proved to be relatively more effective compared to interest based conventional monetary policy. The implications of such findings have established new milestones for the central banks of all the countries, including the muslim majority countries for pursuing interest free Islamic monetary policy with full confidence. Furthermore, there are four major views on Islamic monetary policy and the central banks of the world should choose one of the best methods and views for the greater effectiveness of monetary policy because conventional monetary policy has been less effective in bringing full employment and price stability in recent years and financial crisis has crippled the interest based conventional economic systems quite badly.

Properties of Skyrme force as a residual interaction in beyond-mean-field theories

Abstract In an effort to find an effective interaction that can consistently be used for both the mean-field part and the residual part in beyond-mean-field theories, the properties of the Skyrme interactions as a residual interaction are investigated. The time-dependent density-matrix theory (TDDM) is used as a beyond-mean-field theory and the ground states of $^{16}$O and $^{40}$Ca are calculated using the five standard parametrizations of the Skyrme interaction, which differ in density and momentum dependence. It is found that the Skyrme interaction, which has strong density dependence and weak momentum dependence, induces substantial ground-state correlations comparable to the results of other theoretical calculations.

E-Government in the Republic of Croatia

The goal of this article is to present the development and use of e-government services in the Republic of Croatia. So far, there has been no systematic presentation of Croatian e-government, despite the strong momentum in the development of new electronic services in the last few years. Therefore, this article will be a good basis for further research on Croatian e-government. The article shows the historical development of e-government in Croatia, the current situation and the number of available services in and outside of the e-citizens system (which is the central place of access to Croatian e-government), and the messages that citizens can receive in their user inbox. The intensity of use of all e-government services and the intensity of the use of credentials, depending on their level of security, are shown. A survey was conducted among e-government users about their preferences for using credentials depending on the level of security they offer and ease of use. The results were compared with data on the intensity of use of individual credentials.

Anomalies in the China A-share market

This paper sheds light on the similarities and differences with respect to the presence of anomalies in the China A-share market and other markets. To this end, we examine the existence of 32 anomalies in the China A-share market over the period 2000–2019. We find that value, risk, and trading anomalies carry over to China A-shares. Evidence for anomalies in the size, quality, and past return categories is substantially weaker, with the exception of a strong residual momentum and reversal effect. We document that most anomalies cannot be explained by industry composition, and are present among large, mid, and small capitalization stocks. We are the first to examine the existence of residual reversal, return seasonalities, and connected firm momentum for the China A-share market. We find strong out-of-sample evidence for the former two, but not the latter. Specific characteristics of the China A-share market, such as short-sale restrictions, the prevalence of state-owned enterprises, and the effect of stock market reforms, are examined in more detail. These features do not seem to be important drivers of our empirical findings.

Numerical modelling of an enhanced perpendicular transport regime in the scrape-off layer of ASDEX Upgrade

A desirable scenario for future fusion devices is one in which dissipative processes in the scrape-off layer (SOL) are maximized, aiming to detach the divertor plasma. The access to such a regime in current devices is thought to be correlated to the increase of the perpendicular particle transport in the SOL. In this work we investigated numerically how increasing perpendicular transport globally affects the SOL plasma through the SOLPS-ITER code package. For this we modelled one L-mode discharge, performed at the ASDEX Upgrade tokamak, trying to obtain the most accurate fit to the experimental data at the outer midplane. Studying the plasma solutions and analyzing the resulting momentum and power balances in the SOL allowed to characterize how enhancing perpendicular SOL transport leads to the experimentally observed phenomena, i.e. the formation of a density shoulder at the midplane and the partial detachment of the divertor plasma. The results suggest that strong momentum losses caused by the increase of transport are able to explain the qualitatively observed detachment in the modelled discharge. The concurrent enhanced ionization of neutrals resulting from divertor recycling, triggered by an increase of radial energy transport in the SOL, can be invoked as a cause for the shoulder formation.

Hedging demand and market intraday momentum

Hedging short gamma exposure requires trading in the direction of price movements, thereby creating price momentum. Using intraday returns on over 60 futures on equities, bonds, commodities, and currencies between 1974 and 2020, we find strong market intraday momentum everywhere. The return during the last 30 minutes before the market close is positively predicted by the return during the rest of the day (from previous market close to the last 30 minutes). The predictive power is economically and statistically highly significant, and reverts over the next days. We provide novel evidence that links market intraday momentum to the gamma hedging demand from market participants such as market makers of options and leveraged ETFs.

A high-fidelity numerical study on the propulsive performance of pitching flexible plates

In this paper, we numerically investigate the propulsive performance of three-dimensional pitching flexible plates with varying flexibility and trailing edge shapes. We employ our recently developed body-conforming fluid-structure interaction solver for our high-fidelity numerical study. To eliminate the effect of other geometric parameters, only the trailing edge angle is varied from 45° (concave plate), 90° (rectangular plate) to 135° (convex plate) while maintaining the constant area of the flexible plate. For a wide range of flexibility, three distinctive flapping motion regimes are classified based on the variation of the flapping dynamics: (i) low bending stiffness KBlow, (ii) moderate bending stiffness KBmoderate near resonance, and (iii) high bending stiffness KBhigh. We examine the impact of the frequency ratio f* defined as the ratio of the natural frequency of the flexible plate to the actuated pitching frequency. Through our numerical simulations, we find that the global maximum mean thrust occurs near f*≈1 corresponding to the resonance condition. However, the optimal propulsive efficiency is achieved around f* = 1.54 instead of the resonance condition. While the convex plate with low and high bending stiffness values shows the best performance, the rectangular plate with moderate KBmoderate is the most efficient propulsion configuration. To examine the flow features and the correlated structural motions, we employ the sparsity-promoting dynamic mode decomposition. We find that the passive deformation induced by the flexibility effect can help in redistributing the pressure gradient, thus, improving the efficiency and the thrust production. A momentum-based thrust evaluation approach is adopted to link the temporal and spatial evolution of the vortical structures with the time-dependent thrust. When the vortices detach from the trailing edge, the instantaneous thrust shows the largest values due to the strong momentum change and convection process. Moderate flexibility and convex shape help to transfer momentum to the fluid, thereby improving the thrust generation and promoting the transition from drag to thrust. The increase in the trailing edge angle can broaden the range of flexibility that produces positive mean thrust. The role of added mass effect on the thrust generation is quantified for different pitching plates and the bending stiffness. These findings are of great significance to the optimal design of propulsion systems with flexible wings.

Patterns of Non-governmental Organization (NGO) Participation in the Management of Major Infectious Diseases in China

The purpose of this article is to promote the participation of non-governmental organizations in the management of major infectious diseases in China. We intend to analyze and evaluate the management methods, functions, behaviors, and funding methods of NGOs involved in the prevention and control of infectious diseases in China through various levels of theory and empirical analysis: evaluation and formal judgment of various methods and backgrounds. Government agencies are involved in evaluating the effectiveness of major infectious disease prevention and control in China. It is worth paying full attention to social forces facing sudden public crises, especially non-governmental organizations. The strong momentum of the epidemic has encouraged all actors in society to cooperate and work efficiently and orderly in the prevention and control of infectious diseases.

Validation of a morphology adaptive multi-field two-fluid model considering counter-current stratified flow with interfacial turbulence damping

Stratified flows are one of the most important multiphase flow regimes for safety analyses of the loss-of-coolant accident in pressurized water reactors. The present paper considers simulations of an isothermal counter-current stratified flow case in the channel of the WENKA (Water Entrainment Channel Karlsruhe) experiment using a morphology adaptive multi-field two-fluid modelling framework. A consistent momentum interpolation approach is applied together with the partial elimination algorithm, as it is required for strong momentum coupling, which enforces the no-slip condition at the interface and mirrors the behaviour of a homogeneous model. To model the turbulent flow conditions near an interface, the framework is extended with a turbulence damping model based on the damping scale formulation from the literature, which is introduced into the k-ω SST (Shear Stress Transport) turbulence model. The presented modelling approach is validated with experimental data for the pressure difference and vertical profiles of volume fraction, velocity and turbulent kinetic energy. Results of a mesh sensitivity study of the model are presented. Simulations were performed on two- and three-dimensional models of the channel geometry. Two turbulence damping strategies are investigated: symmetric, with damping in both phases, and asymmetric with damping only in the gas phase. The comparison shows that the asymmetric approach offers improved prediction of turbulent kinetic energy on the liquid side of the interface, but with a cost of diminished accuracy of the predicted velocity profiles on the gas side.

The 52-week High Momentum Strategy and Economic Policy Uncertainty: Evidence from China

ABSTRACT This is the first study to examine the 52-week high momentum strategy that takes economic policy uncertainty (EPU) into account. Empirically, we find significant 52-week high momentum in China, the second-largest stock market in the world, and our findings confirm the results of the US. We hypothesize that anchoring biases could explain the 52-week high momentum and generate significant momentum profits in low EPU periods. The empirical results show strong 52-week high momentum in low EPU periods; there is virtually no momentum when EPU is high, which supports our prediction. Further investigations show that there are no long-run reversals for the 52-week high momentum, and the negative impact of EPU on the 52-week high momentum decreases and eventually vanishes over the long term. All evidence supports the hypothesis that the 52-week high momentum is attributed to anchoring biases, especially when we consider EPU.

Performance Improvement of a Centrifugal Compressor for the Fuel Cell Vehicle by Tip Leakage Vortex Control

Heightened interests have been laid at the preliminary design and optimization of the centrifugal compressor for the fuel cell vehicle. The centrifugal compressor for fuel cell vehicle is driven by a high-speed motor; however, the limit of the motor speed makes the flow passage of the impeller long and narrow, which leads to a serious tip leakage loss. Serious tip leakage loss deteriorates the compressor performance. In this paper, 3-D numerical simulations were carried out with the aim of investigating the tip leakage loss in a prototype centrifugal compressor for a 100 kW fuel cell stack. The results revealed that the mixing loss caused by the interaction between the tip leakage vortex and the downstream tip leakage flow contributed to the major part of the tip leakage loss. The path of the tip leakage vortex almost followed the streamwise direction, while the downstream tip leakage flow exhibited strong circumferential momentum, which referred to the fact that they were nearly orthogonal. Therefore, a flow control approach, which was realized by enhancing the blade loading around the leading edge of blade tips in this paper, was proposed to decrease the interaction angle between the tip leakage vortex and the downstream tip leakage flow and then mitigate mixing loss by changing the flow direction of the tip leakage vortex. The results showed a smaller interaction angle was achieved in the optimized impeller compared with the baseline one. Meanwhile, the efficiency was also improved by 1.30% at design condition and the maximum efficiency improvement could be up to 10% at large mass flow condition of 92 000 r/min. Being manufactured and tested, the optimized compressor was proved to achieve an isentropic efficiency of 75.84% at design condition.

Have trend-following signals in commodity futures markets become less reliable in recent years?

Various trend-following trading rules have been shown to be valuable for predicting market directions and thus the formulation of investment strategies. However, recent equity market research has provided striking evidence that the predictive power of such rules appears to diminish over time due to increased investor attention and lowered arbitrage barriers. Given that trend-following rules are also very successful and have been widely used in futures markets, we analyze whether a similar effect can be observed for commodity futures contracts. Using a trend regression approach based on time-varying success ratios, we detect significantly higher predictive accuracy for cross-sectional than for time-series strategies. In addition, with the exception of a few commodities, we find no significant trending behavior in trading rule reliability. These results, which are robust in a variety of settings, indicate strong momentum stability in futures markets and justify the application of this class of trading rules in commodity futures investing.

Convective core sizes in rotating massive stars

Context. Spectroscopic studies of Galactic O and B stars show that many stars with masses above 8 M⊙ have been observed in the Hertzsprung-Russell (HR) diagram just beyond the main-sequence (MS) band, as predicted by stellar models computed with a moderate overshooting. This may be an indication that the convective core sizes in stars in the upper part of the HR diagram are larger than predicted by these models. Aims. Combining stellar evolution models and spectroscopic parameters derived for a large sample of Galactic O and B stars with the inclusion of brand-new information about their projected rotational velocities, we reexamine the question of the convective core size in MS massive stars. Methods. We computed a grid of 120 different stellar evolutionary tracks with three initial rotations at solar metallicity (Z = 0.014), spanning a mass range from 7 to 25 M⊙, and combining different values for the initial rotation rate and overshooting parameter. For the rotating models, we considered two cases, one with a moderate and one with a strong angular momentum transport, the latter imposing a solid body rotation during most of the MS phase. We confront the results with two observed features: the position of the terminal age main sequence (TAMS) in the HR diagram and the decrease of the surface rotation when the surface gravity decreases at the end of the MS phase. Results. We confirm that for stars more massive than about 8 M⊙, the convective core size at the end of the MS phase increases more rapidly with the mass than in models computed with a constant step overshoot chosen to reproduce the main sequence width in the low mass range (around 2 M⊙). This conclusion is valid for both the cases of non-rotating models and rotating models either with a moderate or a strong angular momentum transport. The increase of the convective core mass with the mass obtained from the TAMS position is, however, larger than the one deduced from the surface velocity drop for masses above about 15 M⊙. Although the observations that are available at present cannot determine the best choice between the core sizes given by the TAMS and the velocity drop, we discuss various methods of escaping this dilemma. At the moment, comparisons with eclipsing binaries seem to favor the solution given by the velocity drop. Conclusions. While we confirm the need for larger convective cores at higher masses, we find tensions among different methods for stars more massive than 15 M⊙. The use of single-aged stellar populations (non-interacting binaries or stellar clusters) would be a great asset in resolving this tension.

Anomalies in the China A-share market

This paper sheds light on the similarities and differences with respect to the presence of anomalies in the China A-share market and other markets. To this end, we examine the existence of 32 anomalies in the China A-share market over the period 2000-2019. We find that value, risk, and trading anomalies carry over to China A-shares. Evidence for anomalies in the size, quality, and past return categories is substantially weaker, with the exception of a strong residual momentum and reversal effect. We document that most anomalies cannot be explained by industry composition, and are present among large, mid, and small capitalization stocks. We are the first to examine the existence of residual reversal, return seasonalities, and connected firm momentum for the China A-share market. We find strong out-of-sample evidence for the former two, but not the latter. Specific characteristics of the China A-share market, such as short-sale restrictions, the prevalence of state-owned enterprises, and the effect of stock market reforms, are examined in more detail. These features do not seem to be important drivers of our empirical findings.