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- 저자 : MASAFUMI NAKAGAWA (검색결과 5 건)
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MASAFUMI NAKAGAWA,ARIEL R. MARASIGAN,TAKANORI MATSUKAWA 대한설비공학회 2010 International Journal Of Air-Conditioning and Refr Vol.18 No.4
The use of two-phase ejector in improving the performance of transcritical CO2 refrigeration system needs further experimental verification particularly the effects of its geometrical design. In this study, experimental data were gathered for ejectors with different mixing cross-sectional areas at different operating temperature and pressure. The results have shown that a smaller mixing area yields higher efficiency due to its higher pressure recovery and entrainment ratio, but its advantages are limited to lower ejector inlet pressure Pc. A larger mixing area is required for higher cooling capacity which can be achieved at higher ejector inlet pressure or lower ejector inlet temperature but excessive increase in this area considerably decreases the efficiency of the system. In this study, the ejector with the largest mixing area was the most inefficient and reduced the COP up to 10% compared to most efficient type. It demonstrates the significant effect of ejector's geometrical features, particularly the mixing cross-sectional area and its related geometrical ratio, in the performance of CO2 ejector system. The effect of motive nozzle inlet condition on pressure recovery profile has been more evident for ejector with smaller mixing area while the evaporator temperature has the least effect in the performance of the system. In the conditions used in this study, using ejector yielded a COP improvement of up to 35% compared to the conventional system.
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Nakagawa, Masafumi,Marasigan, Ariel R.,Matsukawa, Takanori The Society of Air-Conditioning and Refrigerating 2010 International Journal Of Air-Conditioning and Refr Vol.18 No.4
The use of two-phase ejector in improving the performance of transcritical $CO_2$ refrigeration system needs further experimental verification particularly the effects of its geometrical design. In this study, experimental data were gathered for ejectors with different mixing cross-sectional areas at different operating temperature and pressure. The results have shown that a smaller mixing area yields higher efficiency due to its higher pressure recovery and entrainment ratio, but its advantages are limited to lower ejector inlet pressure $P_c$. A larger mixing area is required for higher cooling capacity which can be achieved at higher ejector inlet pressure or lower ejector inlet temperature but excessive increase in this area considerably decreases the efficiency of the system. In this study, the ejector with the largest mixing area was the most inefficient and reduced the COP up to 10% compared to most efficient type. It demonstrates the significant effect of ejector's geometrical features, particularly the mixing cross-sectional area and its related geometrical ratio, in the performance of $CO_2$ ejector system. The effect of motive nozzle inlet condition on pressure recovery profile has been more evident for ejector with smaller mixing area while the evaporator temperature has the least effect in the performance of the system. In the conditions used in this study, using ejector yielded a COP improvement of up to 35% compared to the conventional system.
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Building DSMs generation integrating three line scanner(TLS) and LiDAR
Suh Yong-Cheol,Nakagawa Masafumi 대한원격탐사학회 2005 大韓遠隔探査學會誌 Vol.21 No.3
Photogrammetry is a current method of GIS data acquisition. However, as a matter of fact, a large manpower and expenditure for making detailed 3D spatial information is required especially in urban areas where various buildings exist. There are no photogrammetric systems which can automate a process of spatial information acquisition completely. On the other hand, LiDAR has high potential of automating 3D spatial data acquisition because it can directly measure 3D coordinates of objects, but it is rather difficult to recognize the object with only LiDAR data, for its low resolution at this moment. With this background, we believe that it is very advantageous to integrate LiDAR data and stereo CCD images for more efficient and automated acquisition of the 3D spatial data with higher resolution. In this research, the automatic urban object recognition methodology was proposed by integrating ultra highresolution stereo images and LiDAR data. Moreover, a method to enable more reliable and detailed stereo matching method for CCD images was examined by using LiDAR data as an initial 3D data to determine the search range and to detect possibility of occlusions. Finally, intellectual DSMs, which were identified urban features with high resolution, were generated with high speed processing.
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Psychological Predictors of Satisfaction after Lumbar Surgery for Lumbar Spinal Stenosis
Yamamoto Yoshio,Kawakami Mamoru,Minetama Masakazu,Nakagawa Masafumi,Teraguchi Masatoshi,Kagotani Ryohei,Mera Yoshimasa,Sumiya Tadashi,Matsuo Sachika,Kitano Tomoko,Nakagawa Yukihiro 대한척추외과학회 2022 Asian Spine Journal Vol.16 No.2
Study Design: A retrospective study of prospectively collected clinical data. Purpose: To identify preoperative psychological factors associated with patient satisfaction after surgery for lumbar spinal stenosis (LSS). Overview of Literature: Associations between depressive symptoms, anxiety, and worse surgical outcome or patient dissatisfaction have been reported in LSS patients. However, the influence of preoperative pain catastrophizing and fear-avoidance beliefs on postoperative satisfaction is not well understood. Methods: LSS patients who underwent decompression surgery with or without fusion were included. Clinical outcomes were measured before surgery and 6 months postoperatively using the Zurich Claudication Questionnaire (ZCQ); Visual Analog Scale (VAS) of low back pain, leg pain, and leg numbness; Japanese Orthopaedic Association Back Pain Evaluation Questionnaire; and the Medical Outcomes Study 36-item Short-Form General Health Survey (SF-36). The Hospital Anxiety and Depression Scale (HADS), Pain Catastrophizing Scale, and Pain Anxiety Symptoms Scale were used to evaluate psychological status before surgery. Patients were classified as satisfied or dissatisfied with surgery based on a ZCQ satisfaction subscale cutoff score of 2.5. Results: The satisfied and dissatisfied groups contained 128 and 29 patients, respectively. Six months postoperatively, outcome scores for the dissatisfied group were unchanged or worse than preoperative scores (p >0.05). Multivariate logistic regression analysis showed significant associations between dissatisfaction and preoperative low back pain VAS score ≥median (odds ratio [OR], 0.27; 95% confidence interval [CI], 0.10–0.74; p=0.01), preoperative mental health SF-36 score ≥median (OR, 0.26; 95% CI, 0.08–0.89; p=0.03), and preoperative anxiety HADS score ≥median (OR, 3.95; 95% CI, 1.16–13.46; p=0.03). Conclusions: Preoperative less severe low back pain, lower mental health, and higher anxiety are associated with patient dissatisfaction with lumbar surgery, not depression, pain catastrophizing, or fear-avoidance beliefs. Pre- and postoperative psychological status should be assessed carefully and managed appropriately.
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