Enhancement of R1234ze(Z) Pool Boiling Heat Transfer on Horizontal Titanium Tubes for High Temperature Heat Pumps

Low GWP refrigerant R1234ze(Z) is promising candidate of refrigerant used in industrial high temperature heat pumps. The heat exchangers of such heat pumps designed for waste heat recovery systems is exposed to the exhaust containing acid substances. Using titanium as the material can be one solution to prevent oxidation. In this study, pool boiling heat transfer characteristics outside of horizontal titanium tubes were experimentally investigated for R1234ze(Z) at relatively higher temperatures. A plain tube and three enhanced tubes having different fin geometry were tested in a pressure vessel and the bubble behavior was observed. The experiment covers saturation temperatures from 10 to 60 °C and heat fluxes from 0.55 to 79.8 kWm-2. With the plain tube, it was confirmed that the measured heat transfer coefficients on the plain tube agree with the calculated heat transfer coefficients by Jung et al. correlation proposed for other HFC refrigerants within ±15%. The notable difference to the typical material copper is thermal resistance over the tube wall. Because the thermal conductivity of titanium is only 19 W m-1K-1 (that of copper is approximately 360 W m-1K-1), the thermal resistance is onsiderable. Comparing to the plain tube, the tested enhanced tube exhibited 2.8 to 5.1 times higher heat transfer coefficient, on average, in the test range. This could compensate the disadvantage in thermal conductivity for titanium. The enhancement ratio predominantly depends on the saturation temperature and wall heat flux. At conditions of the higher saturation temperatures and lower heat fluxes, where smaller bubbles were observed, the test tube having smaller fin spaces exhibits higher heat transfer coefficient. The experimental results remark the importance of fin geometry optimization to the operation conditions

Deployment of an Autonomous Underwater Vehicle in Ice-covered Sea of Okhotsk : The First Japanese Challenge

第3回極域科学シンポジウム/第35回極域気水圏シンポジウム 11月29日（木） 国立国語研究所 ２階多目的

Status of Nanosatellite Development for Mothership Daughtership Space Experiment by Japanese Universities

We have begun the feasibility study to build a small satellite in the 3kg mass range and in the power range less than 30W since October in 1998, sponsored by National Space Development Agency of Japan (NASDA). This satellite installs three reaction wheels for an attitude control and camera which will demonstrate optical navigation experiment by using image processing. The BBM design status is described in this paper. The components such as a small reaction wheel, electric flash and onboard computer were built. Mothership - daughtership technology and formation flying experiments are planned. New electric propulsion is being developed for small satellite

Incidence of seed migration to the chest, abdomen, and pelvis after transperineal interstitial prostate brachytherapy with loose 125I seeds

<p>Abstract</p> <p>Background</p> <p>The aim was to determine the incidence of seed migration not only to the chest, but also to the abdomen and pelvis after transperineal interstitial prostate brachytherapy with loose ¹²⁵I seeds.</p> <p>Methods</p> <p>We reviewed the records of 267 patients who underwent prostate brachytherapy with loose ¹²⁵I seeds. After seed implantation, orthogonal chest radiographs, an abdominal radiograph, and a pelvic radiograph were undertaken routinely to document the occurrence and sites of seed migration. The incidence of seed migration to the chest, abdomen, and pelvis was calculated. All patients who had seed migration to the abdomen and pelvis subsequently underwent a computed tomography scan to identify the exact location of the migrated seeds. Postimplant dosimetric analysis was undertaken, and dosimetric results were compared between patients with and without seed migration.</p> <p>Results</p> <p>A total of 19,236 seeds were implanted in 267 patients. Overall, 91 of 19,236 (0.47%) seeds migrated in 66 of 267 (24.7%) patients. Sixty-nine (0.36%) seeds migrated to the chest in 54 (20.2%) patients. Seven (0.036%) seeds migrated to the abdomen in six (2.2%) patients. Fifteen (0.078%) seeds migrated to the pelvis in 15 (5.6%) patients. Seed migration occurred predominantly within two weeks after seed implantation. None of the 66 patients had symptoms related to the migrated seeds. Postimplant prostate D90 was not significantly different between patients with and without seed migration.</p> <p>Conclusion</p> <p>We showed the incidence of seed migration to the chest, abdomen and pelvis. Seed migration did not have a significant effect on postimplant prostate D90.</p

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements