Recently, ammonia (NH₃), which has a higher energy density than hydrogen, has gained attention for zero-carbon emission goals in the transportation sector. However, in a conventional internal combustion engine (ICE), NH₃ combustion mechanism is still under investigation. In this paper, to further expand the knowledge on the adoption of NH₃ in ICEs, authors conducted NH₃/gasoline co-combustion experiments in a modified, 17.7:1 compression ratio, naturally aspirated spark-assisted CI engine with sub-chamber. The sub-chamber was chosen in order to enhance the combustion speed of NH₃. In addition, the sub-chamber was equipped with glow and spark plugs to overcome the high auto-ignition temperature of NH₃. Engine performance and NO_X emissions were studied under three different intake air temperatures. During the experiments, NH₃ content was increased gradually where the engine was run under lean conditions. Although higher NH₃ content was achieved compared to our previous work, increasing the intake air temperature resulted in decreased charging efficiency. In addition, corrosion was found on the piston ring after 120 h of operation, negatively affecting the engine performance. Furthermore, NH₃/gasoline co-combustion duration was shortened drastically with the influence of the sub-chamber, where the longest combustion duration under the present conditions was found to be 17°CA.

HIFU treatment has been developed for various diseases because of its minimal invasiveness, and we are now developing a HIFU treatment for varicose veins of the lower extremity. Previous studies have succeeded in occluding rabbit’s veins with HIFU, but the success rate was low (about 10%). Failures were mainly caused by skin burns. When the heating lesion comes close to skin, the absorbed ultrasound energy may cause skin burns. Therefore, it is necessary to study the relationships between HIFU lesions and skin burns to improve the success rate. To visualize heating lesions from HIFU, we used tissue‐mimicking BSA gel phantoms. We tried various concentrations of BSA in gels, and determined 14% BSA as the most suitable for phantoms for experiments. The attenuation coefficient of the gel was 0.73 dB/cm, and the denaturation temperature was $\text{70\hspace{0.17em}°}\mathrm{C}.$ We put the BSA gel phantom in a water tank in which the temperature was kept at $\text{39\hspace{0.17em}°}\mathrm{C},$ and used HIFU exposures at various intensities and irradiation times. After irradiation, we measured the sizes and positions of HIFU‐induced lesions, and the results indicate that the sizes of lesion become larger when the intensitiy rises or irradiation time becomes longer. Furthermore, when the intensity rises and irradiation time becomes longer, the heating lesions move closer to upper surface of the gel, which means skin easily gets burned. Thus we have investigated relationships between HIFU parameters and heated lesions that can be used for further research into HIFU treatment of varicose veins of the lower extremity.