Institute for Future Engineering

Abstract We demonstrate 100 Gbaud data transmission over 500 m of standard multimode fibers (MMFs) (OM2, OM3, and OM4) using a 1060 nm single-mode coupled-cavity vertical-cavity surface-emitting laser (VCSEL) combined with a simple single-mode-fiber (SMF) patch-cord center-launch scheme. The proposed launch configuration preferentially excites the fundamental fiber mode, thereby suppressing higher-order mode propagation and eliminating modal dispersion in legacy MMFs without the need for bulk optics or complex mode conditioning. The employed VCSEL exhibits a 45 GHz small-signal modulation bandwidth, enabling an end-to-end optical link bandwidth exceeding 50 GHz. Consequently, 100 Gbaud transmission over 500 m is successfully achieved for all tested MMF types. These results indicate that 1060 nm VCSEL-based MMF links can provide practical, scalable, and modal-dispersion-free operation, offering a promising solution for cost-effective, high-bandwidth short-reach optical interconnects and bridging the gap between multimode and SMF systems.

Water-related disasters not only directly lead to loss of life and property, but also entrench poverty, widen disparities, and hinder the accumulation of human capital such as education and health, posing a long-term threat to people's livelihoods. The impact is not uniform: the more vulnerable the group, the greater the damage and the slower the recovery. Those lacking assets and social capital, in particular, have been found to recover more slowly, even from disasters of the same scale. Ultimately, this leads to increased poverty and inequality.In recent years, the number of water-related disasters worldwide has increased due to the impacts of climate change and other factors, accompanied by growing economic losses. Against this backdrop, there has been a growing trend to shift the focus of assessments from the traditional emphasis on 'costs of damage and loss' to 'restoring livelihood opportunities and socio-economic activities'. Therefore, it is essential to consider not only the direct damage and loss caused by water-related disasters, such as housing destruction, road inundation, farmland damage and asset loss, but also their medium- to long-term socioeconomic effects, such as widening inequality and the intergenerational entrenchment of poverty. New measurement and evaluation methodologies must also be pioneered.We argue that 'water-related disasters cause direct damage and loss and can also contribute to the widening of socioeconomic inequality, particularly in lower-middle- and low-income countries'. Based on the hypothesis that 'appropriate flood protection investments as climate adaptation measures can contribute to mitigating damage and loss, as well as reducing disparities and strengthening social resilience', we have conducted extensive research and development. This presentation introduces the following: (1) an empirical analysis of the impact of floods on poverty and economic inequality; and (2) an evaluation of climate adaptation measures that enhance social resilience, with a focus on the long-term socioeconomic spillover effects of flood protection investments.

Eating vegetables first at meals may be associated with mental capital, such as resilience and self-esteem; however, the association has not been well-studied. We examined how trajectories in eating vegetables first from Grade 1 to 6 were associated with resilience and self-esteem at Grade 6 among children in Adachi City, Tokyo, Japan. We used data from the Adachi Child Health Impact of Living Difficulty (A-CHILD) study (N = 2654). Resilience and self-esteem were measured using the Children's Resilient Coping Scale reported by parents and the Children's Perceived Competence Scale reported by children, respectively. Group-based trajectory analysis was performed to identify subgroups of eating vegetables first. Four distinct trajectories were identified: "Not eating vegetables first" (N = 1481, 55.8%), "Increase eating vegetables first" (N = 841, 31.7%), "Reduce eating vegetables first" (N = 157, 5.9%) and "Constant eating vegetables first" (N = 175, 6.6%). After adjusting for potential confounders, children in "Constant eating vegetables first" scored higher resilience (d = 0.20, 95% Confidence Interval, CI: 0.004, 0.39) and higher self-esteem (d = 0.27, 95% CI: 0.06, 0.47) than children in "Not eating vegetables first". Eating vegetables first at meals is associated with mental capital among elementary school children. Four trajectory groups can be identified based on the probability of eating vegetables first. Children who "Constant eating vegetables first" from Grade 1 to Grade 6 had higher mental capital scores (resilience and self-esteem) in Grade 6 than children who did "Not eating vegetables first". Eating vegetables first at meals is associated with mental capital among elementary school children. Further research is recommended to explore the mechanism of how eating vegetables first affects child mental capital.

BackgroundClinical evidence on how social network diversity (SND) influences the risk of infection and disease severity during the coronavirus disease 2019 (COVID-19) pandemic remains limited. We aim to investigate the associations between SND and the risk of COVID-19 infection and disease severity using a large-scale longitudinal cohort study.MethodsWe analyzed data from participants in a longitudinal study, the Japan COVID-19 and Society Internet Survey (JACSIS) between 2020 and 2023. The SND score was calculated as the sum of seven distinct types of social networks. COVID-19 infection was assessed as ever infection, and severity was defined as oxygen-requiring admission, using a self-reported questionnaire. Poisson regression with robust standard errors estimated risk ratios (RRs) and 95% confidence intervals (CIs), adjusting for sociodemographic and clinical characteristics.ResultsOf 13,713 participants (mean age 53.2 ± 15.7 years, 46.4% women), 3,251 (23.7%) developed COVID-19, and among infected individuals, 277 (8.5%) required oxygen therapy. Higher SND scores were associated with COVID-19 infection with linear trend (SND score 7 vs. 0: adjusted RR 2.49; 95% CI 2.11–2.95). In contrast, the association between SND score and disease severity followed a U-shaped pattern, with 4–5 SND showing the lowest risk of oxygen-requiring admission (adjusted RR 0.15; 95% CI 0.11–0.30) compared to those with 0 SND.ConclusionWhile higher SND was associated with increased COVID-19 infection risk, moderate social network diversity appeared protective against severe disease outcomes. These findings suggest a complex trade-off between exposure risk and potential health benefits of social networks during infectious disease outbreaks.

This article presents a terahertz (THz) oscillator integrating resonant tunneling diodes (RTDs) within a cavity resonator for enhanced output power in around 0.7-0.8 THz range. Integration of multiple RTD mesas was applied in this oscillator for improvement of RTD size uniformity. We clarified the operation modes in the oscillator having multiple RTDs by multi-port network analysis as many as the RTD mesa numbers. Measurements including frequency, output power, and polarization were conducted to confirm the device operation. The measured oscillation characteristics fit well with the theory. The highest radiated output power was 1.12 mW at 805 GHz, showcasing the potential of high-power THz radiation using the proposed structure.

The paper introduces a microreactor with high thermal insulation properties, which has been developed for integration with standard planar-type solid oxide fuel cells (SOFCs) in portable power generation applications. While planar SOFCs offer high efficiency and energy density, their use has been largely limited to stationary applications due to challenges in thermal management and slow start-up times. Our microreactor overcomes these barriers by providing an effective thermal insulation system, allowing SOFCs to operate efficiently in a compact, portable format. We designed a cantilevered structure using yttria-stabilized zirconia (YSZ) to minimize thermal conduction and combined it with a multilayer insulation (MLI) system to suppress thermal radiation loss. This flexible cantilevered structure prevents cracking under thermal stress and maintains high temperatures up to 700 °C, ensuring reliable operation. Additionally, the MLI system features an inherent safety mechanism: when the insulation structure is damaged by a drill, the loss of thermal insulation causes a rapid temperature drop, bringing the system below the hydrogen explosion threshold temperature within 5 minutes, thus preventing potential hazards. Our prototype successfully demonstrated handheld power generation using a button-type metal-supported SOFC, achieving a rapid start-up time of just 5 minutes and driving a motor. This breakthrough offers a new platform for miniaturized SOFC technology, bridging the gap between stationary and portable energy solutions.

Composite materials made of Ni-Mn-Ga particles and silicone polymer, which exhibit large magnetic field induced strain (MFIS), good cyclic and long-term stabilities, are highly promising for use in actuation and sensing applications. Whereas MFIS of these composites and their individual particles has been thoroughly investigated in our previous research, MFIS of the ensemble of particles, which are crystallographically and spatially aligned in composite samples, known as the particle grid, has not yet been explored. Since MFIS of a particle grid determines the magnetic field induced shape change of the entire composite, it was crucial to determine how the variation in the spatial dimensions of the grid affects the overall shape change of the composite. In this study, we examined the magnetization curves and magnetostrain behavior of particle grids in six composites, with different fillers such as Ni-Mn-Ga and Fe particles, produced through distinct manufacturing schemes. We used a standard vibrating sample magnetometer and an innovative method that utilized X-ray microCT 3D imaging. It was found that applying a magnetic field perpendicularly to the particle chains causes large strains along the main directions of the particle grid, which differ in magnitude from those observed for composites as a whole known from the literature. Both the effect of peculiar MFIS transfer from particles grid to the entire composite and the impact of Fe particles are examined in relation to the spatial distribution of the particles and their interaction with the polymer matrix.