Contamination of soil and groundwater by synthetic volatile organic compounds (VOCs) and hydrocarbons has recently raised public concern. Geophysical techniques are frequently used to characterize contaminated sites and to specify subsurface contaminant plumes in Europe and America, but there have been very few such surveys in Japan. Electromagnetic (EM) induction mapping was applied to investigate a contaminated site on reclaimed land near a harbour in central Japan. The use of EM mapping enabled efficient coverage of a study area in the site and imaging of the subsurface resistivity distribution down to approximately 10 m. In situ direct‐push membrane interface probe (MIP) and electrical conductivity (EC) in situ measurements were also performed as more direct sensing techniques, and the results were compared with soil core samples. The results suggest that the first and second conductive zones mapped by this investigation correspond to clayey soil zones that act as barriers to prevent the infiltration of contaminants. In addition, the in situ MIP measurements and laboratory analyses indicate multiple occurrences of contamination by VOCs and oil. Although EM mapping was not able to clearly specify a contaminant plume, it was demonstrated as a useful technique to delineate the infiltration pathways of contaminants by illustrating the subsurface distributions of clayey zones. In addition, the combination of direct‐push in situ measurements and EM mapping is demonstrated as an essential characterization strategy to verify the interpreted resistivity structure and to determine the relationship between the heterogeneous resistivity and contaminant distribution.
The Joint Photographic Experts Group (JPEG) baseline system, which is scheduled to be standardized in 1992, is applied to character images, and the characteristics of the application are investigated. The JPEG system is suitable for continuous-tone images, however, continuous-tone images are usually accompanied by characters. The image quality of characters is investigated on various magnitudes of quantization tables and the deterioration mechanisms are discussed. A method ofimage quality improvement that is accomplished by density transformation after decoding is proposed and its effects are confirmed.
Discrete coding transform (DCT) coding is a highly efficient coding method for still images with continuous intensity. It has a feature that a drastic image compression can be realized. Among the coding methods considered by JPEG for international standardization, it is adopted as the most basic baseline system which is a cooperative organization of C U l T and ISO. However, the method is an irreversible coding.When the codingldecdig is applied iteratively to the image once coded and decoded, the image deterioration progresses due to the accumulation of the error. The major causes of the error accumulation are the quantization of the transform coefficient after DCT and the rounding off of the value when the intensity is converted to the integer value in the decoding. This paper shows theoretically the following property. When the quantization step Q satisfies a certain condition and if the image after codingldecoding stays within the range that can be represented by the same number of bits as the original image, no further image deterioration takes place in the following sense. When the decoded *Presently with "IT Integ. Business Service Headquarters.1 image is encoded again using the same quantization table, the result is the same as the previous value. When the image after coding/decoding is outside the range that can be represented by the number of bits of the original image, the value must be restricted.Thus, it is not necessarily true that the DCT transform coefficient of the image after encoding the image is the same as in the previous image. However, it is seen by the result of simulation that even in such a case, the process converges by a finite number of iterative codings, with only a slight deterioration of the signal-to-noise (SN) ratio.
Recently, the number of IoT devices has increased, and this trend has been extended to home appliances (e.g. air conditioners, washing machines, refrigerators, etc.) and equipment (e.g. storage batteries, photovoltaics, etc.). There are mainly two architectures regarding to IoT conversion of the appliances installed in these houses. Specifically, they are "IoT devices connect to a server on the Internet via a controller" and "IoT devices connect to a server on the Internet directly". In this paper, these architectures are compared and it is shown that what kind of usage each architecture is effective.
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