Sensor based sorting is one of the physical separation technology, which detects physical properties of a moving object without contact, identifies its material instantaneously by analyzing the detected information, and separates it mechanically according to the identification result. This separation technology can handle relatively large particles of nonferrous metal, alloy, plastic, glass, paper, wood etc. Recently, social interest in this technology has been growing because various sensors and data analysis devices have been rapidly upgraded. In this review, recent trends of the sensor based sorting in resource recycling are summarized based on the sensor types of NIR, Optical, XRT, XRF, LIBS, Laser 3D etc. The contents of this review are mainly referred from the proceedings of Sensor Based Soring 2012 that is one of the renowned international conferences on this technology.
Infrasound induced by blasting in a limestone mine propagates to the houses in a neighboring village and vibrates their windows, doors, furniture and so on. This infrasound causing vibration becomes an apparent problem for the limestone mine near a village. The most effective way to reduce the vibration is to reduce the blasting scale, but this cannot be performed because of low efficiency for mining. Another effective way is to shift and reduce the dominant frequency of infrasound by changing the delay time of blasting caps so that it may not overlap the resonance frequencies of vibrated objects, but the necessary conditions to do so have not been shown. In this paper, in order to propose the necessary conditions for setting an optimal delay time of blasting caps to reduce the vibration, the infrasound of many patterns of blasting was measured in the face of Ube-Isa Limestone Mine and at a neighboring house of the mine. At the neighboring house, the windows vibration was also measured. From the analyses of these measured data, it was found that the longer delay time of blasting caps is necessary to reduce the lower frequency component causing a large vibration, and shorter one is necessary to shorten the duration of blasting and reduce the resonant vibration. Then, in order to satisfy these conflicting conditions, a varied delay time of blasting caps was proposed and tested. As a result, the windows vibration was reduced 60% in total energy and 24% in maximum displacement compare to the minimum vibration of usual blasting using a fixed delay time of blasting caps.
In the previous paper, based on the summarized experimental results, long-term strength (failure criterion at extremely low loading-rate) was proposed. The simplest form of the long-term strength was σ1 = aσ3 where σ1 and σ3 were major and minor principal stresses, and constant 'a' varied from 2 to 6 depending on rock. For validation of the proposed failure criterion, rock stresses were plotted on σ1 and σ3 diagram. It was found that 86 data except one were plotted under the line (σ1=4σ3). After the previous paper was published, Okubo et al. conducted push-in test in which a failed rock sample was compacted in a steel cylinder. The envelope of Mohr's stress circles through the test were approximated byτ= Aσ0.7. Under this curve, it was considered that strength of the failed sample was recovered up to a certain extent. More than 150 data of rock stresses were newly added to examine the long-term strength. It was found that almost all Mohr's circles were plotted under the curve τ = 2σ0.7. This was the better result than the previous one, σ1=4σ3. As stated in the previous paper, it is reasonable to consider that, in relatively stable rock mass, rock stress is maintained at a certain value lower than a long-term strength. If so, this result supports the validity of the newly proposed long-term strength, τ = 2σ0.7.
On Feburuary 22, 2012, the WTO case of China's export restrictions on raw materials was settled as the Appellate Body report was adopted. The report decided that China's export restraints were inconsistent with its commitments under several agreements.This was the first case that the Appellate Body made a judgement on a case dealing with export restrictions. This paper examines effects of the WTO dispute settlement process for this case using the metal price data. We first review the WTO dispute settlement process and a brief history of the China's export restrictions case. This WTO case is important by two reasons. First, the WTO had been mainly dealing with import restrictions that might prevent smooth trade between nations. Secondly, the targeted commodities were mineral resources neccessary for the wide range of manufactural products. Hence the judgement would probably give a significant impact on many industries. Then, we evaluate the effects of the WTO dispute settlement process by event studies of alminium and zinc prices. We find that the alminium price is not affected, however, the zinc price fell down when the Appellate Body report was adopted. The results of alminium and zinc suggest that the effect of the WTO dispute settlement process might depend on the difference of the production shares of China.
Soil contamination by arsenic is becoming a serious environmental problem worldwide. In this study, a series of experiments were performed to deepen the understanding on the behavior of arsenate in the water-kaolinite-MgO system, with the final objective of evaluating the use of MgO-based materials as an arsenate immobilization agent in soils. Leaching tests performed with leaching solutions of various pH levels and ionic concentrations at a solidliquid ratio of 1:10(w/v)showed that the addition of sufficient amount of MgO effectively immobilized arsenate below 0.01 mg-As/L(the permissible level for leaching tests in Japan)against the exposure to pH 4.0 acid rain for 100 years. Also, experiments using diffusion cells demonstrated that the arsenate desorbed from kaolinite was quickly re-immobilized by MgO addition. These experimental results overall demonstrate that the addition of MgObased materials is a quite effective soil treatment for quick immobilization of arsenate, and that the immobilization effectiveness is long-lasting against exposure to acid rain. However, the MgO dosage needs to be carefully determined considering the decreased capability of kaolinite as an arsenate adsorbent at high pH conditions.