When producing fluid from an unconsolidated sandstone reservoir or producing fluid with high viscosity such as an oil sand, sand production may cause well damage and reduce production rate. Therefore sand control is a very important factor for an efficient and economical fluid production in the above situation.
This paper discussed experimental results on mechanical sand control methods with a screen (wire gauge) or gravel (glass beads) obtained through one dimensional flow model that visualized sand grain movement. Following conclusions were obtained.
(1) Sand production could be controlled by a screen having a larger slot width than sand grain size. This was because the sand bridge was formed on screen slot surface.
(2) The maximum screen slot width was four or five times larger than the 50 percentile sand grain size.
(3) It was observed that there existed an optimum screen width which could control sand and keep minimum pressure loss in laminar or turbulent flow respectively.
(4) It could be noted that screen (wire gauge) could control sand better than gravel (glass beads) from our experimental results.

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現在の音声認識技術では周辺にノイズがあると認識率が低下してしまう。そこで、標準パターンにあらかじめ外来ノイズに類似したノイズを混入することで認識率の低下を防ぐことができることがわかっている。
そこで様々なノイズに対してバタチャリア距離を用いたクラスタリングを行い、ノイズのグループ分けを行った。そして、そのグループ内で平均スペクトルのみでなく、分散を考慮した代表ノイズを選定し、それを標準パターンに混入することでグループ内のノイズによる認識率の低下をより防げることがわかった。

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High pressure multi-stage pump is one of the most important machinery in various plants. Due to the high rotational speed, there are cases where excessive vibration problems occur. Especially, the self-excited vibration arises from the fluid force, which exists within the clearance of the oil film bearings and balancing drum (annular seal). Therefore, it is important to evaluate the stability limit（onset of self-excited vibration）at the design stage. However, the accuracy of the calculation tool is not sufficient at present. Thus, a special measurement tool is needed to analyze the phenomenon of actual equipments. For this reason, we aim at developing an excitation system to evaluate the stability limit by utilizing an active magnetic bearing as an exciter. First, we devised an excitation theory based on Bently-Muszynska model. According to the theory, the stability limit can be evaluated by rotor natural frequencies, and fluid average velocity within the clearance of bearings and balancing drum. In order to measure these parameters, we applied the system to excitation tests, which included the rotating test in air, and in water, respectively. The difference between the tests is whether the fluid force in the balancing drum exists or not. Through the test results, the balancing drum had a significant effect on the rotor stability, and the self-excited vibration occured at the intersection of the natural frequency and fluid average velocity in the balancing drum. Moreover, the resulting frequency（0.72×rotational speed）matched the fluid average velocity (0.73×rotational speed) in the balancing drum.

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In this study, energy absorption property of braided composite pipe was investigated. The braided composite pipes with different braiding angle, the number of laminations and cross-sectional shape were produced and the relationship between the amount of energy absorption and a fracture aspect was clarified. It was clarified that energy absorption was improved under condition that fiber fracture was caused by opening the composite layers both into inside and outside without causing backing. Further, it was found that absorbed energy for bending of the composite was improved by adopting a cross sectional shape with lager moment of inertia of area and aligning the fiber bundle in the circumferential direction.

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The metals contained in a solid biomass fuel form ash after combustion in a furnace, which lowers the thermal efficiency and causes clinker problems. Therefore, there is a great merit if demineralization can be carried out when raw materials are crushing to make pellets or briquettes. In this study, bamboo, which is a promising biomass resource, is used as a sample, was washed with water and hydrochloric acid. The influences of washing method（washing in static water, washing with stirrer, washing with ultrasonic waves）, sample grain size and hydrochloric acid concentration on ash removal, potassium and iron removal in the ash were investigated. And the influence of washing method was compared to that with cypress, which is one of the wood sample. As a result, with the bamboo sample, the amount of ash was greatly reduced by washing with static water for 5 min., and a higher ash removal effect was observed in both by washing with stirrer and with ultrasonic waves. Ash removal effects between washing with stirrer and with ultrasonic waves were almost the same. On the other hand, with the cypress sample, washing with ultrasonic waves showed a higher ash removal effect than that with stirrer. Almost no effect of hydrochloric acid concentration and the sample grain size on ash removal with the bamboo sample was observed in the scope of the present study. It was found that washing with water has a great effect to remove potassium from the bamboo sample. It was observed that iron in bamboo samples was hardly removed by washing with water, but decreased by using hydrochloric acid.

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Because horizontal multi-stage pumps have journal bearings and a balancing piston with narrow gap, it is needed to prevent self-excited vibrations caused by fluid forces in these gaps. For the rotor system, because it is challenging to find the stability limit with a strict model (1 D-FEM), it is better to reduce degree of freedom by fixing nodes of journal bearings and the balancing piston when one is looking to improve the stability limit. This paper suggests a method for finding the stability limit by 2 DOF model, and provides factors affecting the stability limit for horizontal multi-stage pumps. First, the rotor shape and the stiffness and damping of journal bearings and the balancing piston are configured and the rotor system is reduced to 2 DOF by constrained mode synthesis method based on the configurated shape and coefficients. By comparing the solutions calculated with 2 DOF and 1D-FEM, it is confirmed that 2 DOF models are suitable for unstable vibration analysis. Then, the average whirl λ_eqΩ is calculated by applying Bently-Muszynska model to the coefficients of the journal bearings and the balancing piston and it is concluded that the natural frequency ω_n becomes equal to the average whirl λ_eqΩ at the stability limit. Finally, the influence of the natural frequency ω_n and the average whirl λ_eqΩ on the stability limit is analysed for different cases.

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