Study on absorption/desorption characteristics of a metal hydride tank for boil-off gas from liquid hydrogen

We have been performing research on the Totalized Hydrogen Energy Utilization System (THEUS) which has applications to commercial buildings and a planned added function of supplying energy to stations for hydrogen and electric vehicles. In that case we will utilize liquid hydrogen transported from a hydrogen station and all Boil-Off Gas (BOG) will be recovered in THEUS’s metal hydride tanks. It is known that BOG is chiefly composed of para-hydrogen, which has different thermo-physical properties from normal hydrogen. It has been reported that some metal hydride alloys work as a catalyst to accelerate the para-ortho conversion and the conversion proceeds relatively fast in the case of La–Ni₅. The conversion is considered to be an endothermic reaction. A misch metal (Mm)-Ni₅ metal hydride alloy, which contained La and Ni, was used in our THEUS metal hydride tank. To examine the effect of the para-ortho conversion on the THEUS operation, we investigated the absorption/desorption characteristics of the metal hydride tank with BOG. We confirmed that the effect of the heat of conversion was very small and BOG could be treated as normal hydrogen for practical application.     

Expression of a liver-specific function by a hepatoblastoma cell line cocultured with three-dimensional endothelialized tubes in collagen gels

A human hepatoblastoma cell line, Hep G2, showed albumin production activity, a hepatic function, when cocultured with three-dimensional endothelialized tubes in collagen gels. The albumin production rate of the collagen-based liver-like constructs increased with increasing length of the endothelialized tube in the construct.     

Pulverization mechanism of hydrogen storage alloys on microscale packing structure

In-situ and transient visualizations of the packing structure of a hydrogen storage alloy bed are carried out using an X-ray computed tomography (CT) system. The packing structure is clearly observed on the microscale using the CT system. When the alloy bed is subjected to hydrogen absorption–desorption cycles, the pulverization progresses from the lower to the upper regions of the bed. After several hydrogen absorption–desorption cycles, the packing structure in the lower region of the bed changes and the microstructural void decreases slightly. Based on these results, we propose a pulverization mechanism of the packed bed in which the friction between particles affects the pulverization process.     

Numerical simulation of the hydrogen storage with reaction heat recovery using metal hydride in the totalized hydrogen energy utilization system

Numerical simulation of a hydrogen storage tank of a Totalized Hydrogen Energy Utilization System (THEUS) for application to commercial buildings was done to verify the practicality of THEUS. THEUS consists of a fuel cell, water electrolyzer, hydrogen storage tank and their auxiliary machinery. The hydrogen storage tanks with metal hydrides for load leveling have been previously experimentally investigated as an important element of THEUS. A hydrogen storage tank with 50 kg AB5 type metal hydride was assembled to investigate the hydrogen-absorbing/desorbing process, which is exothermic/endothermic process. The goal of this tank is to recover the cold heat of the endothermic process for air conditioning, and thus improve the efficiency of THEUS. To verify the practical effectiveness of this improved system, we developed a numerical simulation code of hydrogen storage tank with metal hydride. The code was validated by comparing its results with experimental results. In this code the specific heat value of the upper and lower flanges of the hydrogen storage tank was adjusted to be equal to the thermal capacity of the entire tank. The simulation results reproduce well the experimental results.     

Bird detection and species classification with time‐lapse images around a wind farm: Dataset construction and evaluation

Collisions of birds, especially endangered species, with wind turbines is a major environmental concern. Automatic bird monitoring can be of aid in resolving the issue, particularly in environmental risk assessments and real‐time collision avoidance. For automatic recognition of birds in images, a clean, detailed, and realistic dataset to learn features and classifiers is crucial for any machine‐learning‐based method. Here, we constructed a bird image dataset that is derived from the actual environment of a wind farm and that is useful for examining realistic challenges in bird recognition in practice. It consists of high‐resolution images covering a wide monitoring area around a turbine. The birds captured in these images are at relatively low resolution and are hierarchically labeled by experts for fine‐grained species classification. We conducted evaluations of state‐of‐the‐art image recognition methods by using this dataset. The evaluations revealed that a deep‐learning‐based method and a simpler traditional learning method were almost equally successful at detection, while the former captures more generalized features. The most promising results were provided by the deep‐learning‐based method in classification. The best methods in our experiments recorded a 0.98 true positive rate for bird detection at a false positive rate of 0.05 and a 0.85 true positive rate for species classification at a false positive rate of 0.1.     

Development of index of social activities for the elderly

In order to develop indices of social activities for the elderly, two surveys with 2 year intervals were conducted on the same 5,201 elderly subjects in four areas in Japan using a self-administered questionnaire. Social activities were defined as "activities which required contact with society" and were measured by 4 major facets of social activities, which were based on 21 questions relating to job activity, socially-plated activities, learning activities, and personal activities. The results were as follows; 1. The Wilcoxon scores in indices for 4 facets were given in sex and age groups. 2. Means of scores of indices increased with the degree of social activities from a subjective judgment. 3. Rank correlation coefficients between indices in two surveys were 0.60-0.71 for the persons whose answers were "no" to the question "did degrees of your activities change over the two years?" 4. Differences between indices in two surveys were higher in the persons with answers of "increase" to the above question than those with answers of "no", and were lower in those with answers of "decrease". These findings suggest that indices are available for assessing social activities as indicated by the reproducibility, validity and responsiveness found in this study.