M. Mohamad, A. Hagishima, N. Ikegaya, J. Tanimoto, A. Omar
This paper reports the results of flow field analysis within and above a two-dimensional street canyon with various overhang lengths using large-eddy simulation (LES). Simulations were conducted for a constant canyon aspect ratio of W/H = 3, where W is the street width and H is the building height. Three different overhang lengths were simulated with P = 0H, 0.5H, and 1H in order to derive the mean and instantaneous flow characteristics. The results are compared with wind tunnel experiments for validation. The LES results of the mean flow with the P = 0H condition agree fairly well with the wind tunnel data. However, profiles of the standard deviation for the streamwise and vertical velocity components show large discrepancies at all measured locations. In addition, an increase in overhang length on both building facades significantly modifies the in-canyon flow pattern by limiting the penetration of the bulk flow into the canyon layer.
{"title":"Aerodynamic effect of overhang on a turbulent flow field within a two-dimensional street canyon","authors":"M. Mohamad, A. Hagishima, N. Ikegaya, J. Tanimoto, A. Omar","doi":"10.15017/1525830","DOIUrl":"https://doi.org/10.15017/1525830","url":null,"abstract":"This paper reports the results of flow field analysis within and above a two-dimensional street canyon with various overhang lengths using large-eddy simulation (LES). Simulations were conducted for a constant canyon aspect ratio of W/H = 3, where W is the street width and H is the building height. Three different overhang lengths were simulated with P = 0H, 0.5H, and 1H in order to derive the mean and instantaneous flow characteristics. The results are compared with wind tunnel experiments for validation. The LES results of the mean flow with the P = 0H condition agree fairly well with the wind tunnel data. However, profiles of the standard deviation for the streamwise and vertical velocity components show large discrepancies at all measured locations. In addition, an increase in overhang length on both building facades significantly modifies the in-canyon flow pattern by limiting the penetration of the bulk flow into the canyon layer.","PeriodicalId":11722,"journal":{"name":"Engineering sciences reports, Kyushu University","volume":"11 1","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2015-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87767899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bathymetric data with a resolution of 5 min called gbscs5 have been compiled for a shelf region shallower than 200 m in the South China Sea by referring to paper charts, electronic charts, and trackline sounding data. Through a comparison between the new dataset and existing datasets (etopo5, etopo1, gebco08), characteristics of each dataset, including the existence of artificial features derived from erroneous sounding data or a conversion error of depth units, were documented for each dataset. It was found that small-scale bathymetric features observed along the shelf edge in gebco08 bathymetry are bounded by survey lines and were likely to be a spurious figure generated when applying a high-order interpolation scheme. Tidal simulations conducted with changing bathymetries have shown that the newly compiled dataset will produce smaller deviation from observed values than the existing bathymetries. While all four datasets analyzed in this study were found to be suitable for estimating overall tidal features of the South China Sea, a care must be taken when applying the tidal model results to a particular coastal region.
{"title":"Compilation and validation of bathymetric data for the South China Sea with an emphasis on shallow region","authors":"K. Uehara","doi":"10.15017/1456040","DOIUrl":"https://doi.org/10.15017/1456040","url":null,"abstract":"Bathymetric data with a resolution of 5 min called gbscs5 have been compiled for a shelf region shallower than 200 m in the South China Sea by referring to paper charts, electronic charts, and trackline sounding data. Through a comparison between the new dataset and existing datasets (etopo5, etopo1, gebco08), characteristics of each dataset, including the existence of artificial features derived from erroneous sounding data or a conversion error of depth units, were documented for each dataset. It was found that small-scale bathymetric features observed along the shelf edge in gebco08 bathymetry are bounded by survey lines and were likely to be a spurious figure generated when applying a high-order interpolation scheme. Tidal simulations conducted with changing bathymetries have shown that the newly compiled dataset will produce smaller deviation from observed values than the existing bathymetries. While all four datasets analyzed in this study were found to be suitable for estimating overall tidal features of the South China Sea, a care must be taken when applying the tidal model results to a particular coastal region.","PeriodicalId":11722,"journal":{"name":"Engineering sciences reports, Kyushu University","volume":"324 1","pages":"7-13"},"PeriodicalIF":0.0,"publicationDate":"2013-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77584233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Weiting Chen, K. Ogiwara, 荻原 公平, Koichiro Koge, 神家 幸一郎, K. Tomita, 冨田 健太郎, K. Uchino, 内野 喜一郎, Y. Kawai, 河合 良信, コウヘイ ハギワラ, コウイチロウ コウゲ, ケンタロウ トミタ, キイチロウ ウチノ, ヨシノブ カワイ
The dependences of the VHF plasma parameters on the gas pressure and power were examined by using the Laser Thomson scattering method, where the VHF plasma was produced in the high pressure region by the balanced power feeding method. It was found that the balanced power feeding method provides a high electron density plasma with low electron temperature at high pressures. This characteristics were confirmed by calculations using a 2-dimensional simulation code.
{"title":"Investigation of VHF Argon Plasma at High Pressure by Balanced Power Feeding Using Laser Thomson Scattering","authors":"Weiting Chen, K. Ogiwara, 荻原 公平, Koichiro Koge, 神家 幸一郎, K. Tomita, 冨田 健太郎, K. Uchino, 内野 喜一郎, Y. Kawai, 河合 良信, コウヘイ ハギワラ, コウイチロウ コウゲ, ケンタロウ トミタ, キイチロウ ウチノ, ヨシノブ カワイ","doi":"10.15017/1397755","DOIUrl":"https://doi.org/10.15017/1397755","url":null,"abstract":"The dependences of the VHF plasma parameters on the gas pressure and power were examined by using the Laser Thomson scattering method, where the VHF plasma was produced in the high pressure region by the balanced power feeding method. It was found that the balanced power feeding method provides a high electron density plasma with low electron temperature at high pressures. This characteristics were confirmed by calculations using a 2-dimensional simulation code.","PeriodicalId":11722,"journal":{"name":"Engineering sciences reports, Kyushu University","volume":"67 1","pages":"6-11"},"PeriodicalIF":0.0,"publicationDate":"2013-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77355646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Rusinov, M. Sakamoto, 坂本 瑞樹, H. Zushi, 図子 秀樹, R. Ohyama, K. Honda, T. Tanabe, 田邉 哲朗, N. Yoshida, 吉田 直亮, ミズキ サカモト, ズシ ヒデキ, リョウヘイ オオヤマ, コウイチロウ ホンダ, テツオ タナベ, ナオアキ ヨシダ
Deuterium retention and trapping in tungsten plasma sprayed layers after low energy plasma irradiation was investigated by means of thermal desorption technique. Plasma irradiation at low temperatures ( 650 K) showed significant increase of the retention in the plasma sprayed layers contrary to the polycrystalline material. Thermal desorption spectra showed extremely high temperatures of the peak positions which are non-typical for the tungsten materials. The possible reasons for such high deuterium retention in the plasma sprayed layers after irradiation at high temperatures and the possible trapping mechanisms are discussed.
{"title":"Deuterium trapping properties of plasma sprayed tungsten layers irradiated by low energy and high flux plasma","authors":"A. Rusinov, M. Sakamoto, 坂本 瑞樹, H. Zushi, 図子 秀樹, R. Ohyama, K. Honda, T. Tanabe, 田邉 哲朗, N. Yoshida, 吉田 直亮, ミズキ サカモト, ズシ ヒデキ, リョウヘイ オオヤマ, コウイチロウ ホンダ, テツオ タナベ, ナオアキ ヨシダ","doi":"10.15017/24650","DOIUrl":"https://doi.org/10.15017/24650","url":null,"abstract":"Deuterium retention and trapping in tungsten plasma sprayed layers after low energy plasma irradiation was investigated by means of thermal desorption technique. Plasma irradiation at low temperatures ( 650 K) showed significant increase of the retention in the plasma sprayed layers contrary to the polycrystalline material. Thermal desorption spectra showed extremely high temperatures of the peak positions which are non-typical for the tungsten materials. The possible reasons for such high deuterium retention in the plasma sprayed layers after irradiation at high temperatures and the possible trapping mechanisms are discussed.","PeriodicalId":11722,"journal":{"name":"Engineering sciences reports, Kyushu University","volume":"27 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77082963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
m was investigated using the helicoid spring specimen technique. The testing temperatures ranged from 423 K to 523 K (0.47 to 0.58 Tm) and the applied stresses from 0.20 to . It was found that under the above conditions, viscous creep of Bingham type occurs, characterized by a threshold stress which decreases with increasing temperature. The activation energy is Qc = 44 7 kJ/mol. No microstructural changes were observed in recrystallized and the as-crept specimens. The measured creep rates were found to be four orders faster than that predicted by Coble creep model.
{"title":"Creep behavior inb a fine-grained Al -5356 alloy at low stress and intermediate temperature","authors":"Junjie Shen, K. Ikeda, S. Hata, H. Nakashima","doi":"10.15017/19574","DOIUrl":"https://doi.org/10.15017/19574","url":null,"abstract":"m was investigated using the helicoid spring specimen technique. The testing temperatures ranged from 423 K to 523 K (0.47 to 0.58 Tm) and the applied stresses from 0.20 to . It was found that under the above conditions, viscous creep of Bingham type occurs, characterized by a threshold stress which decreases with increasing temperature. The activation energy is Qc = 44 7 kJ/mol. No microstructural changes were observed in recrystallized and the as-crept specimens. The measured creep rates were found to be four orders faster than that predicted by Coble creep model.","PeriodicalId":11722,"journal":{"name":"Engineering sciences reports, Kyushu University","volume":"244 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2011-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77565022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Oliveira, A. Hagishima, J. Tanimoto, 萩島 理, 谷本 潤, アヤ ハギシマ, ジュン タニモト
An outdoor measurement was performed during fine weather with a scale-model array of cubical obstacles (size 100mm, 25% packing density, lattice-type square layout) that represent an idealized urban tissue. Surface temperature was recorded with high-frequency (10Hz) infrared camera, along with wind speed and solar radiation. Complementarily, air temperature was also measured at three heights in the near-wall region of a block surface using fine-wire thermocouples. Results showed the similarity of distribution between surface temperature and scalar transfer coefficient. We also found that 10s averaging period may be appropriate for the analysis of surface temperature fluctuation affected by turbulent airflow. In the near-wall region under particularly calm wind condition, air temperature fluctuation caused by a hot plume arising from the warmed surface was observed. The method presented in this study seems to be a promising tool to analyze surface temperature characteristics of scale-models in urban climate studies.
{"title":"A scale-model experiment of surface temperature characteristics using an infrared radiation camera","authors":"J. Oliveira, A. Hagishima, J. Tanimoto, 萩島 理, 谷本 潤, アヤ ハギシマ, ジュン タニモト","doi":"10.15017/18934","DOIUrl":"https://doi.org/10.15017/18934","url":null,"abstract":"An outdoor measurement was performed during fine weather with a scale-model array of cubical obstacles (size 100mm, 25% packing density, lattice-type square layout) that represent an idealized urban tissue. Surface temperature was recorded with high-frequency (10Hz) infrared camera, along with wind speed and solar radiation. Complementarily, air temperature was also measured at three heights in the near-wall region of a block surface using fine-wire thermocouples. Results showed the similarity of distribution between surface temperature and scalar transfer coefficient. We also found that 10s averaging period may be appropriate for the analysis of surface temperature fluctuation affected by turbulent airflow. In the near-wall region under particularly calm wind condition, air temperature fluctuation caused by a hot plume arising from the warmed surface was observed. The method presented in this study seems to be a promising tool to analyze surface temperature characteristics of scale-models in urban climate studies.","PeriodicalId":11722,"journal":{"name":"Engineering sciences reports, Kyushu University","volume":"24 1","pages":"1-8"},"PeriodicalIF":0.0,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78412638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Demands for dc current sensors have recently been increasing. We developed a hysteresis-free current sensor based on a magnetic bridge by using magnetic fluid as a core material, which is super-paramagnetic and has no magnetic hysteresis. In the experiment, the core size was 42 mm in outer diameter, 28 mm in inner diameter, and 3.5 mm in height. The sensor became saturated at ±200 A input current, but no hysteresis was observed throughout the whole range of measurement. In a measurement range of ±20 A, the sensitivity was 0.603 mV/A, the linearity error was ±0.7 %, and the temperature error characteristics were -0.2 %/°C from 0 °C to 30 °C. This hysteresis-free current sensor would be useful in energy-efficient power systems to enable accurate current monitoring, especially in dc power-distribution systems.
{"title":"Development of a Current Sensor Based on a Magnetic Fluid Magnetic Bridge","authors":"忠津 孝, 笹田 一郎, T. Tadatsu, I. Sasada","doi":"10.3379/MSJMAG.1104R014","DOIUrl":"https://doi.org/10.3379/MSJMAG.1104R014","url":null,"abstract":"Demands for dc current sensors have recently been increasing. We developed a hysteresis-free current sensor based on a magnetic bridge by using magnetic fluid as a core material, which is super-paramagnetic and has no magnetic hysteresis. In the experiment, the core size was 42 mm in outer diameter, 28 mm in inner diameter, and 3.5 mm in height. The sensor became saturated at ±200 A input current, but no hysteresis was observed throughout the whole range of measurement. In a measurement range of ±20 A, the sensitivity was 0.603 mV/A, the linearity error was ±0.7 %, and the temperature error characteristics were -0.2 %/°C from 0 °C to 30 °C. This hysteresis-free current sensor would be useful in energy-efficient power systems to enable accurate current monitoring, especially in dc power-distribution systems.","PeriodicalId":11722,"journal":{"name":"Engineering sciences reports, Kyushu University","volume":"74 1","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2010-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83434925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. J. Eshraghi, I. Sasada, Jin Mok Kim, Yong-Ho Lee
†We evaluated the thermal conductivity of AlN ceramic plates as a potential material of a thermal guide for cooling SQUID in cryocooler cooled SQUID systems. We found that the AlN ceramic plate does not show a good thermal conductivity at very low temperature. We tried to enhance its thermal conductivity by attaching a lot of thin insulated copper wires in parallel with each other to cover a back plane of the plate. With this enhancement we succeeded to operate a double relaxation oscillation SQUID (DROS) first-order gradiometer. Comparison of measurement results on white noise level between two cases where DROS was attached to a copper plate thermal guide and where it was attached to a modified AlN thermal guide shows almost 5 time reduction in noise floor with the latter plate.
{"title":"AIN ceramic thermal guide for cooling a SQUID and its effect on thermal magnetic noise","authors":"M. J. Eshraghi, I. Sasada, Jin Mok Kim, Yong-Ho Lee","doi":"10.15017/16413","DOIUrl":"https://doi.org/10.15017/16413","url":null,"abstract":"†We evaluated the thermal conductivity of AlN ceramic plates as a potential material of a thermal guide for cooling SQUID in cryocooler cooled SQUID systems. We found that the AlN ceramic plate does not show a good thermal conductivity at very low temperature. We tried to enhance its thermal conductivity by attaching a lot of thin insulated copper wires in parallel with each other to cover a back plane of the plate. With this enhancement we succeeded to operate a double relaxation oscillation SQUID (DROS) first-order gradiometer. Comparison of measurement results on white noise level between two cases where DROS was attached to a copper plate thermal guide and where it was attached to a modified AlN thermal guide shows almost 5 time reduction in noise floor with the latter plate.","PeriodicalId":11722,"journal":{"name":"Engineering sciences reports, Kyushu University","volume":"61 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2009-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85849290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Gocheva, Yuichi Kamimura, T. Doi, S. Okada, J. Yamaki, T. Nishida
{"title":"Direct synthesis of Cryolite type Li3FeF6 and its characterization as positive electrode in Li cell","authors":"I. Gocheva, Yuichi Kamimura, T. Doi, S. Okada, J. Yamaki, T. Nishida","doi":"10.15017/16410","DOIUrl":"https://doi.org/10.15017/16410","url":null,"abstract":"","PeriodicalId":11722,"journal":{"name":"Engineering sciences reports, Kyushu University","volume":"83 1","pages":"7-11"},"PeriodicalIF":0.0,"publicationDate":"2009-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77647054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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