National Graduate Institute for Policy Studies

Distributed space antennas enable large apertures for future space missions. However, on-orbit reconfiguration remains challenging due to complex orbital dynamics and stringent fuel constraints. To address this, we propose a fuel-efficient framework integrating trajectory design and beamforming optimization using sequential convex programming. By jointly optimizing satellite trajectories and beamforming to exploit relative orbital drift, numerical simulations of a fault recovery scenario demonstrate a drastic reduction in fuel consumption (approximately 1/40) compared to conventional control. Furthermore, the method successfully restores the degraded side lobe level, establishing a robust foundation for long-life operations of resource-constrained satellite swarms.

Abstract Innovation indicators show a strong increase in capabilities of latecomer countries in green technologies over the last 20 years. Latecomers have become leading origin of green technology publications, hold 27 per cent of green technology patents and 38 per cent of green technology exports. There is considerable heterogeneity between latecomer countries, indicating that each country follows a specific path that reflects domestic strengths and weaknesses. A review of existing case studies for wind energy, photovoltaics, hydrogen technologies, and (environmentally-friendly) mining technologies shows a set of driving factors for successful latecomer development emerges from typical case studies. We suggest a taxonomy for success factors for green technology latecomer development which consists of characteristics of the specific technology, active demand side and industrial policies of the state, openness to global markets, and exploitation of windows of opportunities with regard to geographical factors.

Abstract Ecological interaction can induce evolutionary diversification of a biological population into distinct multiple populations. Such a process is called evolutionary branching in adaptive dynamics theory. In one-dimensional trait spaces, the existence of an evolutionary branching point ensures evolutionary branching of an asexual monomorphic population in its neighborhood under rare and small mutations. An evolutionary branching point is a convergence stable point (i.e., a point attractor for a monomorphic population through directional selection) that is not an ESS (evolutionarily stable strategy). For analysis of arbitrarily higher-dimensional trait spaces with respect to evolutionary branching induced by convergence stable non-ESSes, this study develops two kinds of criteria. The two criteria, referred to as branching possibility and branching inevitability, are based respectively on the canonical equation of adaptive dynamics theory and on the local Lyapunov function. The branching possibility ensures the existence of evolutionary paths achieving evolutionary branching. The branching inevitability, which corresponds to Fisher’s fundamental theorem of natural selection, ensures steady progress of evolutionary branching through repeated invasions by arbitrary mutants having positive invasion fitnesses, even when the timescale separation between population dynamics and evolutionary dynamics is incomplete. All strongly convergence stable non-ESSes have the branching possibility. All absolutely convergence stable non-ESSes have both the branching possibility and branching inevitability.

Restrictive abortion laws in many African nations are associated with risks such as unsafe procedures and teenage motherhood. This study examines how abortion legalization influences sexual and reproductive health and women's empowerment in South Africa, using a difference-in-differences design. Analyzing variations in birth cohorts and access to health care facilities with abortion services across provinces, the study finds no direct causal impact of the abortion policy on teenage motherhood, fertility rates, early sexual debut, high school completion, or college attendance, though negative associations with teenage motherhood and fertility rates and positive associations with early sexual debut, high school completion, and college attendance, were observed. The study suggests that limited access to health care facilities with abortion services and cultural taboos contribute to underreporting of behaviors. Given these findings, we recommend prioritizing access to contraception and creating supportive environments for adolescent girls living in vulnerable situations, including improved access to health care facilities that offer abortion services.

A tighter monetary policy is generally associated with higher real interest rates on deposits and loans, weaker performance of equities and real estate, and slower growth in employment and wages. How does a household's exposure to monetary policy vary with its age? The size and composition of both household income and asset portfolios exhibit large variation over the lifecycle in Japanese data. We formulate an overlapping generations model that reproduces these observations and use it to analyze how household responses to monetary policy shocks vary over the lifecycle. Both the signs and the magnitudes of the responses of a household's net worth, disposable income and consumption depend on its age.