Analysis of Fuel Cell Stack Performance Attenuation and Individual Cell Voltage Uniformity Based on the Durability Cycle Condition

Based on the dynamic cycle condition test of a 4.5 kW fuel cell stack, the performance attenuation and individual cell voltage uniformity of the proton exchange membrane fuel cell (PEMFC) stack was evaluated synthetically. The performance decay period of the fuel cell stack was 180–600 h, the decrease of voltage and power was evaluated by rate and amplitude. The results show that the performance of the fuel cell stack decreased with the increase of test time and current density. When the test was carried out to 600 h, under rated operating conditions, the voltage attenuation rate was 130 μV/h, and the voltage reduced by 71 mV, with a decrease of 10.41%. The power attenuation rate was 0.8 W/h, with a decrease of 10.42%. The statistical parameter variation coefficient was used to characterize the voltage consistency of individual cells. It was found that the voltage uniformity is worse at the high current density point and with a long-running process. The variation coefficient was 3.1% in the worst performance.

Filtrated Pseudo-Orbit Shadowing Property and Approximately Shadowable Measures

In this paper, it is proved that every diffeomorphism possessing the filtrated pseudo-orbit shadowing property admits an approximately shadowable Lebesgue measure. Furthermore, the C1-interior of the set of diffeomorphisms possessing the filtrated pseudo-orbit shadowing property is characterized as the set of diffeomorphisms satisfying both Axiom A and the no-cycle condition. As a corollary, it is proved that there exists a C1-open set of diffeomorphisms, any element of which does not have the shadowing property but admits an approximately shadowable Lebesgue measure.

Upaya Meningkatkan Kemampuan Mengenal Konsep Warna Melalui Kegiatan Meronce Pada Anak Kelompok B TK Dharma Wanita 2 Mojotengah Kedu Temanggung Semester I Tahun Pelajaran 2017/2018

One of the basic competencies in kindergarten is that children can recognize simple concepts with indicators that children are able to recognize color concepts. Color recognition for children can stimulate the senses of sight, brain, aesthetics, and emotions. Meronce activities are aimed at training children's eye and hand coordination. The rationale for this problem arises is the low ability to recognize the concept of color in Group B TK Dharma Wanita 2 Mojotengah. The purpose of this study was to determine the process of meronce activities to improve the ability to recognize children's color concepts and to determine the magnitude of the increase in the ability to recognize color concepts after resonating activities in Group B children TK Dharma Wanita 2 Mojotengah Kedu Temanggung Semester I Academic Year 2017/2018. The subjects of this study were 15 students of Group B TK Dharma Wanita 2 Mojotengah. The research was carried out from September to October 2017. The data collection methods used were observation, documentation, and interviews. Based on the results of research and discussion, it can be concluded that meronce activities can improve the ability to recognize color concepts in Group B children TK Dharma Wanita Mojotengah 2. This can be seen from the results of increasing the ability to recognize color concepts in Group B children TK Dharma Wanita Mojotengah 2 in The pre-cycle condition was 20% then increased to 46.7% in Cycle I and finally increased in Cycle II by 93.3%, it was proven that the child was able to designate colors, mention or differentiate colors and classify colors.

Application of Ag/AgCl Sensor for Chloride Monitoring of Mortar under Dry-Wet Cycles

An Ag/AgCl electrode used as a corrosion sensor in a reinforced concrete structure is considered as having good application prospect. However, its performance under complex conditions, such as dry-wet cycle condition, is not affirmed. In the current study, the performance of Ag/AgCl as chloride selective electrode in mortar exposed to dry-wet cycle condition was investigated. A simple Ag/AgCl electrode was prepared and fabricated by electrochemical anodization. These Ag/AgCl electrodes were embedded into a mortar specimen with temperature sensors, humidity sensors and anode ladder monitoring system (ALS). After 28 d curing time, the upper surface of mortar specimen was wetted (with 5% NaCl solution) and dried regularly. The obtained results indicate that Ag/AgCl electrode responds to the ingress of chloride ion, sensitively. The chloride ion concentration variation can be reflected by the potential trend. Furthermore, the balance potential of Ag/AgCl electrodes is influenced by dry-wet cycles. Compared with ALS, it demonstrates that Ag/AgCl electrodes are more sensitive to chloride. The research provides the key element for the specific application of Ag/AgCl electrode for corrosion monitoring in the future.