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Now showing items 1 - 12 of 12

  • Evaluation of a Compact Coaxial Underground Coal Gasification System Inside an Artificial Coal Seam

    Su, Fa-qiang   Hamanaka, Akihiro   Itakura, Ken-ichi   Deguchi, Gota   Zhang, Wenyan   Nan, Hua  

    The Underground Coal Gasification (UCG) system is a clean technology for obtaining energy from coal. The coaxial UCG system is supposed to be compact and flexible in order to adapt to complicated geological conditions caused by the existence of faults and folds in the ground. In this study, the application of a coaxial UCG system with a horizontal well is discussed, by means of an ex situ model UCG experiment in a large-scale simulated coal seam with dimensions of 550 x 600 x 2740 mm. A horizontal well with a 45-mm diameter and a 2600-mm length was used as an injection/production well. During the experiment, changes in temperature field and product gas compositions were observed when changing the outlet position of the injection pipe. It was found that the UCG reactor is unstable and expands continuously due to fracturing activity caused by coal crack initiation and extension under the influence of thermal stress. Therefore, acoustic emission (AE) is considered an effective tool to monitor fracturing activities and visualize the gasification zone of coal. The results gathered from monitoring of AEs agree with the measured data of temperatures; the source location of AE was detected around the region where temperature increased. The average calorific value of the produced gas was 6.85 MJ/Nm(3), and the gasification efficiency, defined as the conversion efficiency of the gasified coal to syngas, was 65.43%, in the whole experimental process. The study results suggest that the recovered coal energy from a coaxial UCG system is comparable to that of a conventional UCG system. Therefore, a coaxial UCG system may be a feasible option to utilize abandoned underground coal resources without mining.
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  • Endovascular Aneurysm Repair with Balloon Thrombectomy for Acute Thrombosis of Abdominal Aortic Aneurysm

    Uotani, Kensuke   Hamanaka, Akihiro   Matsushiro, Keigo   Idaka, Erika   Ito, Kiyo   Yamasaki, Yuko   Kushima, Takeyuki   Sugimoto, Takaki   Sugimoto, Koji  

    Acute occlusion of abdominal aortic aneurysm (AAA) is a rare complication and is usually treated with surgical reconstruction. We present a case of acute AAA occlusion that was successfully treated by endovascular aneurysm repair (EVAR) with Fogarty balloon thrombectomy. A 77-year-old man with a history of acute myocardial ischemia presented with limb weakness and coldness. Contrast-enhanced computed tomography showed a 42-mm-diameter infrarenal AAA that was completely thrombosed in the distal portion. The proximal neck of the aneurysm was patent, and its shape was suitable for EVAR. Therefore, we performed balloon thrombectomy of the aortoiliac thrombus that was followed by EVAR. EVAR can be a less invasive alternative than traditional treatment for acute occlusion of AAA.
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  • Effects of pH-Induced Changes in Soil Physical Characteristics on the Development of Soil Water Erosion

    Matsumoto, Shinji   Ogata, Shunta   Shimada, Hideki   Sasaoka, Takashi   Hamanaka, Akihiro   Kusuma, Ginting Jalu  

    Soil water erosion is frequently reported as serious problem in soils in Southeast Asia with tropical climates, and the variations in pH affect the development of the erosion. This study investigated the effects of changes in pH on soil water erosion based on changes in the physical properties of the simulated soils with pH adjusted from 2.0 to 10.0 through artificial rainfall tests. The zeta potential was entirely shifted to positive direction at each pH condition due to Al, Ca, and Mg. In the pH range of 6.0 to 2.0, the aggregation of soil particles resulting from the release of Al3+ from clay minerals and/or molecular attraction between soil particles caused the plastic index (I-P) of the soil to decrease. The decrease in IP led to the development of soil water erosion at the pH range. When the pH exceeded 6.0, the repulsive force generated by the negative charges on soil particles decreased IP, resulting in accelerated erosion by water. The results suggest that changes in pH causes physical properties of the soil to change through changes of the zeta potential in the clayey soil rich in Al, Ca, and Mg, leading to the development of soil water erosion.
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  • Evaluation of Coal Combustion Zone and Gas Energy Recovery for Underground Coal Gasification (UCG) Process

    Su, Fa-qiang   Hamanaka, Akihiro   Itakura, Ken-ichi   Deguchi, Gota   Sato, Kohki   Kodama, Jun-ichi  

    During underground coal gasification (UCG) operations, evaluation of coal gasification cavity evolution and precise control of the underground reactor are important for efficient gasification. It is also essential to estimate the energy recovery of a UCG system and the whole gasification process to ensure an effective combustion and gasification rate. An experimental simulation of UCG using an artificial coal seam comprising a compacted broken coal block was conducted using ex situ UCG models. The main goal of the experiments was the establishment of evaluation methods for the gasification zone and energy recovery during UCG. To investigate the distribution and extent of fracture activity, and to evaluate the propagation of the combustion area in the UCG reactor, we used acoustic emissions (AE) monitoring. This was combined with traditional measurements of temperature variation and product gas content. This paper presents the results of AE analysis of the fracturing activities and damage mechanisms of the coal seam with respect to the UCG operations. From the results of AE source location, we found that the position and area of the crack concentration area, i.e., the gasification zone, can be inferred with comparative accuracy. This is important for in situ practical application of underground coal gasification. In addition, use of the distribution characteristics of AE information over time can also provide advanced warning, and help in timely adjustment of the operational parameters. The results of gas energy recovery were estimated with a proposed stoichiometric method based on measured product gas composition. Quantitative evaluation results include the gas quantities, coal consumption, and heating value yield of the produced synthesis gas. The coal consumption of the obtained energy recovery results also meets the estimated results when calculating the gasification volume with AE source locations (in an error range of about 10%). Therefore, the applied AE monitoring and gas energy recovery approaches may be considered attractive options for evaluating the coal gasification process and developing a safe and efficient UCG system.
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  • High resolution CT findings of pulmonary epithelioid hemangioendothelioma: unusual manifestations in 2 cases.

    Sakamoto, Noriaki   Adachi, Shuji   Monzawa, Shuichi   Hamanaka, Akihiro   Takada, Yoshiki   Hunada, Yasuhiro   Kotani, Yoshikazu   Hanioka, Keisuke  

    Pulmonary epithelioid hemangioendotheliomas (PEH), also known as intravascular sclerosing bronchoalveolar tumor, is a rare vascular tumor of the lung common among young women. Primitive lumena lined by single cells is the characteristic pathologic feature. The endothelial nature of these cells is confirmed by positive staining with factor VIII and CD34. PEH usually presents as single or multiple pulmonary nodules. The present report describes high resolution CT (HRCT) findings of 2 cases with unusual manifestations of PEH. One case was a 54-year-old woman with multiple pulmonary nodules with irregular thickening of both the bronchovascular bundles and perilobular structures, representing intensive lymphangitic spread on HRCT. The other was an 18-year-old woman who had multiple minute peripheral nodules in the lungs bilaterally. These HRCT findings demonstrated the presence of tumor nodules in the lymphatic spaces, which is quite an unusual histologic presentation for this tumor. Both cases also showed hepatic lesions on abdominal CT; the former showing hypoattenuating masses with coarse calcifications and the latter showing multiple tiny calcifications in the hepatic parenchyma. Recognition of these features in the appropriate clinical setting may allow the clinician and the pathologist to consider this rare tumor.
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  • Fundamental Study on Assessment of Soil Erosion by the USLE Method at Rehabilitation Area in Indonesian Coal Mine

    Inoue, Naoya   Hamanaka, Akihiro   Shimada, Hideki   Sasaoka, Takashi   Matsui, Kikuo  

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  • Monitoring and evaluation of simulated underground coal gasification in an ex-situ experimental artificial coal seam system

    Su, Fa-qiang   Hamanaka, Akihiro   Itakura, Ken-ichi   Zhang, Wenyan   Deguchi, Gota   Sato, Kohki   Takahashi, Kazuhiro   Kodama, Jun-ichi  

    In this study, to better simulate underground coal gasification (UCG), an artificial coal seam was constructed to use as a simulated underground gasifier, which comprised coal blocks excavated from the coal seam. This study reports the process and results of three independently designed experiments using coaxial-hole and linking-hole UCG models: (a) a coaxial model using a coaxial pipeline as a gasification channel, (b) a coaxial model using the coaxial pipeline combined with a bottom cross-hole, and (c) a linking-hole model using a horizontal V-shaped cross-hole. In the present work, the fracturing activities and cavity growth inside the reactor were monitored with acoustic emission (AE) technologies. During the process, the temperature profiles, gas production rate, and gas content were measured successively. The results show that AE activities monitored during UCG process are significantly affected by operational variables such as feed gas rate, feed gas content, and linking-hole types. Moreover, the amount of coal consumed during UCG process were estimated using both of the stoichiometric approach and balance computation of carbon (C) based on the product gas contents. A maximum error of less than 10% was observed in these methods, in which the gas leakage was also considered. This demonstrates that the estimated results using the proposed stoichiometric approach could be useful for evaluating energy recovery during UCG.
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  • Stability Control of Retained Goaf-Side Gateroad under Different Roof Conditions in Deep Underground Y Type Longwall Mining

    Zhang, Zhiyi   Shimada, Hideki   Sasaoka, Takashi   Hamanaka, Akihiro  

    Stability of the retained goaf-side gateroad (RGSG) is influenced mainly by the movements of the roof strata near coal seam after coalface passes by. To make effective controlling technology for the stability of the RGSG, we analyze the roof structure over the RGSG to illustrate the mechanism causing the RGSG instability under different roof conditions. We then examine the dynamic evolution of the deformation and abutment stress in the rock surrounding the RGSG during coal seam mining, using the FLAC3D numerical software to reveal the instability characteristics of the RGSG under different roof conditions. Next, corresponding stability controlling technologies for the RGSGs are proposed and tested in three typical deep underground coalmines. Results show that: sink and rotation of the roof cantilever over the RGSG impose severer influence on the stability of the RGSG. The RGSG suffers disturbances three times during the coal-seam mining, and the deformation and abutment stress in the rock surrounding the RGSG increase significantly when the main roof becomes thicker and the immediate roof becomes thinner. Staged support technology involving grout cable bolts has better controlling results of the RGSG stability than that composed of conventional rock bolts, when the RGSG is beneath weak immediate roof with large thickness. Roof structure optimizing technology involving pre-split technology can improve the stability of the RGSG effectively when the RGSG is covered by hard main roof with large thickness directly.
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  • Phase I/II Study of Radiofrequency Ablation for Painful Bone Metastases:Japan Interventional Radiology in Oncology Study Group 0208

    Tanigawa, Noboru   Arai, Yasuaki   Yamakado, Koichiro   Aramaki, Takeshi   Inaba, Yoshitaka   Kanazawa, Susumu   Matsui, Osamu   Miyazaki, Masaya   Kodama, Yoshihisa   Anai, Hiroshi   Hamanaka, Akihiro  

    A prospective multicenter phase I/II trial was performed to evaluate the clinical safety and efficacy of radiofrequency ablation (RFA) for metastatic bone tumors. Thirty-three patients (27 men, 6 women, mean age 61 years) with metastatic bone tumors were enrolled. In phase I, nine patients were enrolled, and the safety of RFA was evaluated. In phase II, 23 patients were included, and an intent-to-treat analysis was performed. The primary endpoint was to evaluate the treatment's safety. The secondary endpoint was to evaluate the efficacy of pain relief at 1 week after RFA. RFA was performed in 32 of 33 enrolled patients. No serious complications were observed during the phase I, so phase II was performed. Four patients exhibited adverse events, including one case each of Grade 3 pain and, Grade 2 hypotension, and one patient developed Grade 1 burns at the grounding pad and puncture site. One patient died of liver failure on day 7 after RFA due to the progression of the primary lesion. The efficacy was excellent (no increase in analgesic dosage, post-RFA VAS score of 0-2 or decreased by not less than 5 compared to before RFA) in 20 patients (60.6%), good (no increase in analgesic dosage, post-RFA VAS score decreased by not less than 2 but by < 5 compared to before RFA) in 3 (9.1%), and poor in 10 patients (30.3%). Thus, the response rate was 69.7%. RFA is a safe and effective method for treating painful metastatic bone tumors.
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  • Study on Control of Wall Deflection in Earth Stepped-Twin Retaining Wall Using Anchor Method by means of Numerical Simulation

    Maehara, Kazuki   Hamanaka, Akihiro   Sasaoka, Takashi   Shimada, Hideki   Sakuma, Seiya  

    The demand for specific earth retaining wall methods is increasing along with the advancement and overcrowding of underground space use such as the presence of adjacent structures in an urban area. To cope with this, the method named earth stepped-twin retaining wall is increasingly being applied. However, there is a concern about the workplace if the earth pressure causes a heaving and pressing phenomenon from both ends of the retaining wall in the earth stepped-twin retaining wall. Therefore, we proposed the application of an anchor method that contains the inner and outer walls by using numerical simulation. The effects of the difference in soil properties, the horizontal distance between the outer and inner walls, and the depth of the outer wall embedment on the anchor were investigated. The results of this study show that the wall deflection of the inner wall could improve by adopting the anchor support. Besides, it was found that the inner wall can be efficiently suppressed by adopting the hybrid system with anchors and struts according to the soil properties, horizontal distance, and the depth of the outer wall.
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  • Effect of Injection Flow Rate on Product Gas Quality in Underground Coal Gasification (UCG) Based on Laboratory Scale Experiment:Development of Co-Axial UCG System

    Hamanaka, Akihiro   Su, Fa-qiang   Itakura, Ken-ichi   Takahashi, Kazuhiro   Kodama, Jun-ichi   Deguchi, Gota  

    Underground coal gasification (UCG) is a technique to recover coal energy without mining by converting coal into a valuable gas. Model UCG experiments on a laboratory scale were carried out under a low flow rate (6 similar to 12 L/min) and a high flow rate (15 similar to 30 L/min) with a constant oxygen concentration. During the experiments, the coal temperature was higher and the fracturing events were more active under the high flow rate. Additionally, the gasification efficiency, which means the conversion efficiency of the gasified coal to the product gas, was 71.22% in the low flow rate and 82.42% in the high flow rate. These results suggest that the energy recovery rate with the UCG process can be improved by the increase of the reaction temperature and the promotion of the gasification area.
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  • [IEEE 2013 8th International Forum on Strategic Technology (IFOST) - Ulaanbaatar, Mongolia (2013.06.28-2013.07.1)] Ifost - Fundamental study on revegetation of post mine surface by paper mulberry in open cut mine

    Hamanaka, Akihiro   Inoue, Naoya   Shimada, Hideki   Sasaoka, Takashi   Matsui, Kikuo   Miyajima, Ikuo  

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