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The purpose of the study is to evaluate whether nighttime luminosity sourced from the Defense Meteorological Satellite Program-Operational Linescan System satellite sensors is a suitable proxy for measuring poverty in Africa.

Our study performs wavelet coherence analysis to investigate the time-frequency synchronization between the nightlight data and “income-to-wealth” ratio for 39 African countries between 1992 and 2012.

All-in-all, the authors find that approximately a third of African countries produce positive synchronizations between nighttime data and “income-to-wealth” ratio and hence conclude that most African countries are not at liberty to use nighttime data to proxy conventional poverty statistics.

In differing from previous studies, the authors examine the suitability of nightlight intensity as a proxy of poverty for individual African countries using much more rigorous analysis.

This study aims to investigate the dynamic co-movement and interconnection among 69 security investment indices in China using the multi-time scale framework.

The authors first use the multiple coherence analysis method to exhibit the degree of relationships among the variables under study. In addition, the wavelet multiple correlation and wavelet multiple cross-correlation analyses are used to examine the time-frequency synchronization interdependence structure among the variables.

From the empirical findings, one may infer less opportunity for portfolio diversification at higher time scales. Obviously, at these scales, the authors find that the 69 Chinese investment indices generate a simple security investment class, as indicated by higher interconnection between the indices.

Further research can increase the sample size to re-investigate the empirical relationship for security investment indices.

In the nutshell, the results demonstrate the potential for Chinese investors to invest in security investment indices to earn from portfolio diversification at lower time frequencies. The Chinese investment market indices under study yield further opportunities of portfolio diversification toward the short-term investors than the long-term investors.

To the best of the authors’ knowledge, this is the first paper to examine the dynamic co-movement and interconnection for security investment indices in China.

To the best of our knowledge, no study has examined credit cycle synchronizations in the context of emerging economies. Studying the credit cycles synchronization across BRICS (Brazil, Russia, India, China and South Africa) countries is crucial given the magnitude of trade and financial integration among member counties. The enormity of the trade and financial linkages among BRICS countries and growth spillovers from emerging economies to advanced and low-income countries provide the rationale and motivation to study the synchronization of credit cycles across BRICS.

The study investigates the credit cycles coherence across BRICS economies from 1996Q2 to 2020Q4. The synchronization analysis is done using the noval wavelet approach. The analysis examines not only the coherence but also the extent of credit cycle synchronization that varies across frequencies and over time among different pairs of nations.

The authors find heterogeneity in the credit cycles' synchronization among the member nations. China and India are very much in sync with the other BRICS countries. China's high-frequency credit cycle mostly leads the other countries' credit cycles before the global financial crisis and shows a mix of lead/lag relationships post-financial crisis. Interestingly, most of the time, India's low-frequency credit cycles lead the member countries' credit cycles, and Brazil's low frequency credit cycle lag behind the other BRICS countries' credit cycles, except for Russia. The results are crucial from the macroprudential policymaker's perspective.

The empirical design is applicable to a similar set of countries and may not directly fit each emerging economy.

The findings will help understand the marked deepening of trade, technology, investment and financial interdependence across the world. BRICS acronym requires no introduction, but such analysis may help understand the interaction at the monetary policy level.

This is the first study that highlights the need to understand the credit variable interactions for BRICS nations.

The studies on international housing markets have not modeled frequency domain and focused only on the time domain. The purpose of the present research is to fill this gap by using the state-of-the-art econometric technique of wavelets to understand how differences in the horizon of analysis across time impact international housing markets’ relationship with some of the key macroeconomic variables. The purpose is to also analyze the direction of causation in the relationships.

The author uses the novel time–frequency analysis of international housing markets’ linkages to the macroeconomic drivers. Unlike conventional approaches that do not distinguish between time and frequency domain, the author uses wavelets to study house prices’ relationship with its drivers in the time–frequency space. The novelty of the approach also allows gaining insights into the debates that deal with the direction of causation between house price changes and macroeconomic variables.

Results show that the relationship between house prices and key macroeconomic indicators varies significantly across countries, time, frequencies and the direction of causation. House prices are most related to interest rates at the higher frequencies (short-run) and per capita income growth at the lower frequencies (long-run). The role of industrial production and income growth has switched over time at lower frequencies, particularly, in Finland, France, Sweden and Japan. The stock market’s nexus with the housing market is significant mainly at high to medium frequencies around the recent financial crisis.

The present research implies that in contrast to the existing approaches that are limited to the only time domain, the frequency considerations are equally, if not more, important.

Results show that interested researchers and analysts of international housing markets need to account for the both horizon and time under consideration. Because the factors that drive high-frequency movements in housing market are very different from low-frequency movements. Furthermore, these roles vary over time.

The insights from the present study suggest policymakers interested in bringing social change in the housing markets need to account for the time–frequency dynamics found in this study.

The paper is novel on at least two dimensions. First, to the best of the author’s knowledge, this study is the first to propose the use of a time–frequency approach in modeling international housing market dynamics. Second, unlike present studies, it is the first to uncover the direction of causation between house prices and economic variables for each frequency at every point of time.

THREE PROJECTED Collision Avoidance Systems have been described in the January, February and March issues. They are, respectively, the EROS II L‐band time‐frequency‐based system, the Honeywell YG1081 C‐band Collision Warning System (CWS) and SECANT, a non‐synchronous L‐band system.

THE airborne Eros II Collision Avoidance System (CAS) designed and produced by McDonnell Douglas Corporation is actuated when the computer calculates the aircraft is within 25 sec of or ½ mile of another aircraft whichever event occurs first. At the same time, the pilot of one of the aircraft gets a command to climb while the pilot of the other aircraft is instructed to descend, thus avoiding a potential mid‐air collision.

This study aims to investigate the time-frequency comovement between wheat futures traded on three US markets (Chicago Board of Trade (CBOT), Kansas City Board of Trade (KCBOT) and Minneapolis Grain Exchange (MGE)) at different maturities and a global equity index.

As they allow to trace transitional shifts over time and across different frequency bands, this paper relies on continuous wavelet tools to investigate the time-frequency comovement among wheat and global stock markets.

The results show an increase in wheat futures prices at all maturities and a weak integration level within each wheat market during the subprime crisis. Moreover, the wavelet power spectra maps show high wheat and equity price volatility at different time scales and for various subperiods. Furthermore, the continuous wavelet coherence highlights time-frequency-varying comovements between the markets considered, which become particularly high during times of crisis.

The results provide market participants with a better understanding of the nature as well as the magnitude of the relationship between the global financial market and different wheat markets at different maturities and during tranquil and crisis periods. Indeed, from investors' perspective it is important to understand how markets are segmented or integrated during tranquil and crisis periods in order to better assess risks, diversify portfolios and implement more effective hedging strategies. As for regulators, a better understanding of the level of integration of different markets would further help refine macroprudential policies, and thus strengthen financial stability and resilience.

This paper enriches the existing literature by investigating the time-frequency comovement between wheat and a global equity market. Indeed, the dynamics between stock and wheat markets across different nearest to maturities have not been widely explored by previous studies.

The purpose of this study was to evaluate the effects of repetitive transcranial magnetic stimulation (rTMS) at different frequencies on working memory (WM) and neuroelectric activity in rats.

Three rTMS protocols involving different frequencies were applied to rats, and 16-channel local field potentials (LFPs) and spikes were recorded from the prefrontal cortex (PFC) of rats in each group during the WM task. First, the behavior of rats during the T-maze task was analyzed, and then, the firing rate of spikes and the energy of the θ-band and γ-band in LFPs when rats performed the WM tasks were calculated. Finally, the spectral coherence between LFPs and spikes was analyzed by wavelet transform.

The results showed that rats in the stimulation groups needed fewer days than those in the control group to reach the task correction standard during the WM experiment (p < 0.05). High-frequency rTMS increases the firing rate of spikes and the degree of synchronization of LFPs-spikes in the θ-band and γ-band in the WM process.

This study showed that high-frequency rTMS can improve the spatial learning ability of rats, which might be due to the increased neuronal excitability of the PFC and the enhancement of co-coding between different modes of neural signals. This study is helpful for understanding the neuroregulatory mechanism of rTMS and will provide a reference for the selection of a suitable frequency for TMS treatment.

IN THIS article the evolution of formation flight technology is traced including discussion of the primary characteristics of three specific station keeping system concepts developed by Lockheed‐Georgia. One of the most significant aspects of the overall formation flight problem is that of stability of the formation in a dynamic environment. Detailed simulation studies of the dynamic station keeping geometry have been performed, and the results are presented in the form of fundamental formation flight stability criteria. The extension of present‐day technology to development of formation flight systems for short range aircraft such as helicopters and V/STOL transports is considered briefly.