Effect of compressive force on the performance of a proton exchange membrane fuel cell

The effect of the compressive force on the performance of a proton exchange membrane fuel cell has been examined experimentally. The performance has been evaluated on two polarization regions of the cell: ohmic and mass transport. Cell voltage and current density as a function of pressure were measured under constant load and various inlet air humidity conditions. The pressure distribution on the surface of the gas diffusion layer was measured using a pressure detection film and the results show that increasing the pressure improves the performance of the cell. The improvement of the cell voltage in the ohmic region was found to be greater than that in the mass transport region, whereas for the cell current density, the mass transport region exhibited higher change. The increase in the cell specific power in the ohmic and mass transport regions, as pressure increases from 0 to 2MNm-2, is estimated to be 9 and 18mWcm−2, respectively. However, the fuel cell performance in these two regions declined dramatically when excessive pressure (≥5 MNm−2) was applied. The mass transport region proved to be more susceptible to this sharp decline under excessive pressure than the ohmic region

Influence of Section Spacing on Reliability of Abdominal Computed Tomography in Early Stage Non-Seminomatous Testicular Tumor

Comparison of reliability of CT with contiguous and non-contiguous scan reading was performed in 100 consecutive patients with a non-seminomatous testicular tumor and lymph nodes less than 20 mm at CT. The patients underwent primary lymphadenectomy and histologic examination of removed nodes. Ten mm thick slices at adjacent 10 mm intervals were used and non-contiguous reading was based on sections with uneven numbers. Reading of non-contiguous scans led to drop in sensitivity from 71% to 66% compared with contiguous scans when 5 mm was used as criterion for abnormal node size. Corresponding decrease was from 47% to 39% with the 10 mm criterion and from 37% to 26% with the 15 mm criterion. Other parameters were only slightly influenced by the scan reading technique. The benefit of contiguous as opposed to non-contiguous scanning was small in the present series. </jats:p