Various low toxicity substances are contained in the high functional electronic products in recent years. Although there is a little quantity of low toxicity substances in each electronic product, total amount of them has been increasing by the mass production of electronic products. This means they tends to diffuse into environment and it also results in the loss of valuable metals.In this work, a substance flow analysis (SFA) on low toxicity substances in used cellular phones as a typical example of high functional electronic commodity was carried out based on the actual condition of disposal which was acquired by the questionnaire applied to users and composition of cellular phone analyzed by ICP and EPMA. The amount of some scattered low toxicity substances has been estimated. It was pointed out that establishment of the recycling system of cellular phones including used ones stored by users is very important in the view point of the avoidance of low toxicity substance diffusion and recovery of valuable elements.
This study describes the design and benefits of a new type of caisson called the "precast form caisson". Many recently developed caisson construction methods use full-precast plates, whose joints are poor in durability and load bearing capacity. Design and construction methods that c0mpensate for these weaknesses by using full-precast members are very c0mplicated, making them inferior in cost and effectiveness. The authors overcame those drawbacks by using a precast form concrete caisson that has half-precast members and a reinforced concrete c0mposite structure. The caisson is made of H-steel and c0mprises a high-durability precast form and an RC precast form, which are filled with super-plasticized concrete. In July 1999, we produced a precast form caisson measuring 14 m long, 12 m wide and 11 m high in T0mak0mai Port, to verify the method's effectiveness and econ0mic feasibility.key Words : precast form caisson, construction method, highly durable permanent formwork, reiforced concrete permanent formwork, embossed H-section steel
Many types of breakwater have been developed to withstand the emormous wave force of a deep sea area.However, most have not proven viable in terms of constructability, economy and so on. The sloping slit caisson is expected to overcome these problems. It acts to dissipate wave energy by a front perforated wall and a wave chamber.The downward force acting on the slope increases the caisson's stability.This study describes the efficiency, design and construction method, and then explains the results of actual construction.
After the East Groin of Ishikari Bay New Port subsided, we gathered data on the average caisson height and on the significant wave height measured at the surface where the water depth was 24 m in the sea offshore of the port. These two types of data were compared to investigate the relationship between the subsidence and waves. Also, we examined the causes of the subsidence and countermeasures based on the results of post-subsidence surveys, including an onsite survey. The examination revealed that when high waves cause subsidence that progresses to some extent, there was no major subsidence after that extent. The post-subsidence soil survey confirmed that the scour occurred after the subsidence. The onsite survey indicated that mat installation was an effective countermeasure against scour.
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