National Institute of Technology, Kochi College

This paper proposes a method to drive the inductor current in Triangular Current Mode (TCM) without detecting the bottom current. Detecting the bottom current is difficult at high switching frequencies due to the bandwidth limitations of the shunt resistor and peripheral circuits. The proposed method achieves TCM operation by calculating the turn-on and turn-off times. However, if the bottom current is not detected, current errors may occur due to parameter errors and voltage fluctuations within a switching cycle. The proposed method compensates for the current error by proportional control based on the detected filter inductor current. The operation of the proposed method is verified through simulation and experiment. The experimental results confirm that the gridtied inductor current operates in TCM and that the filter inductor current follows the reference value. The total harmonic distortion (THD) of the filter inductor current under this condition is $\mathbf{2. 8 \%}$.

ABSTRACT At metallicities lower than that of the Small Magellanic Cloud, it remains essentially unexplored how fossil magnetic fields, forming large-scale magnetospheres, could affect the evolution of massive stars, thereby impacting the fundamental building blocks of the early Universe. We extend our stellar evolution model grid with representative calculations of main-sequence, single-star models with initial masses of 20 and 60 M$_\odot$, including appropriate changes for low-metallicity environments ($Z = 10^{-3}$–$10^{-6}$). We scrutinize the magnetic, rotational, and chemical properties of the models. When lowering the metallicity, the rotational velocities can become higher and the tendency towards quasi-chemically homogeneous evolution increases. While magnetic fields aim to prevent the development of this evolutionary channel, the weakening stellar winds lead to less efficient magnetic braking in our models. Since the stellar radius is almost constant during a blueward evolution caused by efficient chemical mixing, the surface magnetic field strength remains unchanged in some models. We find core masses at the terminal-age main sequence between 22 and 52 M$_\odot$ for initially 60 M$_\odot$ models. This large difference is due to the vastly different chemical and rotational evolution. We conclude that in order to explain chemical species and, in particular, high nitrogen abundances in the early Universe, the adopted stellar models need to be under scrutiny. The assumptions regarding wind physics, chemical mixing, and magnetic fields will strongly impact the model predictions.

The catalytic decarboxylation of aromatic carboxylic acids provides an alternative route to generate aryl metal species in situ without using organometallic compounds. Herein, a cationic iridium-catalyzed decarboxylation of aromatic carboxylic acids through CO2 extrusion is described. The substrate scope is broad, and the reaction proceeds even in the presence of various functional groups. Additionally, the potential utility of the reaction was demonstrated in the decarboxylative hydroarylation of bicyclic alkenes and decarboxylative fluorination. More information can be found in the Research Article by Tomohiko Shirai et al.

Invited for the cover of this issue are Tomohiko Shirai and co-workers at the National Institute of Technology Kochi College and their collaborators at Chuo and Hokkaido Universities. The image depicts how asymmetric decarbonylative C-C bond formation by the Ir/S-Me-BIPAM complex takes precedence over aldehyde decarbonylation. Read the full text of the article at 10.1002/chem.202104347.

The method of making OH radicals generated by the collapse of ultrafine bubbles as an indicator when applying ultrasound was examined as the method of identifying ultrafine bubbles less than 1 μm in diameter under the presence of mixed solid nanoparticles. First, potassium iodide (KI) method was used to evaluate OH radicals. Since difference in absorbance due to OH radicals generated by the collapse of ultrafine bubbles is very small when using air as contained gas, evaluation using the KI method was difficult; however, a distinct difference in absorbance was confirmed by increasing the amount of OH radicals generated by using ozone as contained gas. Moreover, the higher the ultrasound frequency, the greater the difference in absorbance. On the other hand, a luminescence phenomenon related to the collapse of ultrafine bubbles by ultrasound was confirmed with sonoluminescence observation, confirming further that the luminescence intensity of water added with solid particles of the same diameter and number density as those of ultrafine bubbles is smaller than that of ultrafine bubble water.

In the growth study of agricultural crops, it is important to measure photon flux density (PFD) on each wavelength region such as ultraviolet, blue, green, red, and far-red. In our previous study, a simple band-spectra quantum meter was developed using photovoltaic (PV) cells, however the space resolution for measurement area was low owing to the large device size. Developed band-spectra quantum meter with the size of 70 mm length × 35 mm width × 10 mm height was configured using ultra-small PV cells and optical bandpass filters. A cover with the role to reduce the light reaching to the PV cells was equipped to maintain linear correlation between short-circuit current output of the ultra-small PV cells and outdoor solar radiation intensity. Band-spectral PFD according to the irradiated light wavelength was obtained from the developed quantum meter irradiated with green light.

Silane type surface penetrants were applied to young age mortar for the purpose of shortening the construction period when silane type surface penetrants were applied to the newly constructed concrete structure and its strength characteristics were investigated. As a result, when the silane type surface penetrants were applied to mortar with age of 7 days, slight increase in strength was observed compared with applying to 28 days of age or compared with the untethered mortar. In addition, in order to estimate this cause, mass change and pore diameter distribution were also measured. As a result, it was considered that the reason why the mortar strength increases at the age of young age was due to the curing effect with the internal water by applying silane type surface penetrants at young age. Therefore, it was considered that there were few problems of strength by applying silane type surface penetrants to the mortar at the age of young age.

This paper describes the “2016 KOSEN Space Camp,” which is an introductory education program on space technology for students enrolled at the various KOSEN colleges of technology in Japan. The camp was conducted twice, the first time on September 3–6, 2015 and the second time on September 1–4, 2016 at the Marine Park Niihama. Approximately 40 students and more than 10 teachers participated in the camp on each of the two occasions when it was held. The activities in the camp included a lecture by an eminent scientist; the study of basic rocket theory; model rocket experiments; and the development, analysis, and presentation of CanSat satellite model experiments. This unique education program provided by aerospace scientists and engineers is a KOSEN concept and product.