Piezoelectric bedload impact sensor (PBIS) for particle size distribution.

A multi-channel Piezoelectric Bedload Impact Sensor (PBIS) is developed to estimate mass and particle-size distribution of bedload in low to moderate slope natural streams. The PBIS’s stand-alone design with a sufficiently large data memory facilitates continuous long-term monitoring for low-scale bedload measurements. The design concept of PBIS is based on a hypothesis that particle collision energy on the PBIS plate increases with hydraulic energy and particle size. Thus, particle size can be differentiated by the number of impulses registered in four different threshold channels. The feasibility of PBIS was evaluated by developing a calibration model based on laboratory flume experiments. Two different types of experiment were conducted: (1) individual particle experiment and (2) multi-size particle experiment. The individual particle experiment results indicated that hydraulic condition affected the mode of bedload particle motion. The mean impulse rate per particle is expressed as a function of bed shear stress, t. In addition, the represented particle sieve size range of each threshold channel was determined based on the fractional impulse ratio per unit mass by the particle sieve size class. The multi-size particle experiment results indicated that multi-particle interaction and signal interference from consecutive particle impacts on the PBIS plate caused a notable reduction of registered impulses in channel 1 from approximately 700 impulses per minute. The bias between individual and multi-size particle experiment results caused by multi-particle effects were expressed by a function of bed shear stress, t, and mean impulse rate, Rj, in each PBIS threshold channel. The adjusted calibration coefficient is a coefficient of linear equation to convert registered impulses to mass of particles retained in the represented particle sieve size classes of each channel. The adjusted calibration coefficients for each channel were estimated using the two-dimensional response surface methodology (RSM) with two variables, bed shear stress, t, and mean impulse rate, Rj. This study was enough to show the feasibility of the multi-channel PBIS to obtain mass and particle-size distribution of small gravel bedload. However, many issues associated with the calibration model are still remained beyond this study. First of all, the calibration model was developed based on laboratory flume experiments conducted in a well-controlled small-scale environments. Second, from the comparison between the actual and the estimated values, it was found that two inherent error factors which can cause overestimate are imbedded in the linear calibration model of PBIS. Third, two major assumptions for the model, an equal fractional bedload particle-size distribution and the law of large number, always have a distinction from chaotic phenomena in natural bedload transport. Because of that, the most preferential request will be the field application

Self-assembled Electronic Nose based on Air-bridge-structured Nanowire Junction Arrays

Materials Science EngineeringIn this article, we introduce a facile synthesis and characterization of alternatively driven dual nanowire arrays with single crystalline nanostructures of ZnO and CuO that capable of reliably discriminating between three gases such as hydrogen (H2), carbon monoxide (CO), and nitric dioxide (NO2) in air. In the Part 1, we describe the fabrication process for multiple nanowires species (ZnO and CuO) growth via chemical vapor deposition at 773-873 K, without the incorporation of foreign atoms. This process can be simply achieved by a direct and simultaneous heating of metallic film with Zn and Cu followed by a conventional lithography. It was clearly observed that there is no chemical cross-contamination between them, separated by 5 µm, during the growth. Additionally, the sensing properties for the single crystalline nanowires of ZnO and CuO are then tested and compared for their ability to distinguish three gases (H2, CO and NO2) in air, which they were able to do unequivocally. In the Part 2, we also introduce a strategy for creating an air-bridge-structured nanowire junction array platform for their ability to distinguish three gases (H2, CO and NO2) in air. Alternatively driven dual nanowire species of ZnO and CuO on single substrate are used and decorated with metallic nanoparticles to form two dimensional microarray, which do not need to consider the post fabrications. Each individual nanowires in the array form n-n, p-p and p-n junctions act as electrical conducting path for carrier. The adsorption of gas molecules to the surface changes the potential barrier height formed at the junctions and the carrier transport inside the straight semiconductors, which provide the ability of a given sensor array to differentiate among the junctions. The sensor were tested for their ability to distinguish three gases (H2, CO and NO2), which they were able to do unequivocally when the data was classified using linear discriminant analysis.ope

The national identity of a diaspora: A comparative study of the Korean identity in China, Japan and Uzbekistan.

This research concerns the collective identity of Korean diasporas who have settled in China, Japan, and post-Soviet central Asia, with special attention to Uzbekistan. The main research considers how the Korean diasporas define their collective identities in their respective host states, and the political implications of the constitution of such identities. The means by which a collective identity is secured vary, depending on a diaspora's relations and interactions with its homeland and host state, and vision of its own community. Despite sharing many features common to not being assimilated by host societies, the three Korean diasporas have maintained their distinctive identities in each case under this study. A diaspora's identity is thus to be understood as having a particular nature, which I see as a third type of national identity. I argue that the features of diasporas are generated by the following three factors: the homeland, the hostland, and the diaspora organisations. A diaspora identity is reflected in the intrinsic quandaries it experiences within this triangular structure. These quandaries are created by fundamental tensions; such as the dilemma between seeking a fuller degree of inclusion and maintaining autonomy, the psychological conflicts between the awareness of the need for collective resistance against assimilation and the aspiration for overcoming sub-national collectivity, and the difficulties that arise from the process of accepting a different national identity while not detached from their ancestral motherland. The Korean diasporas are nearing the point of creating self-determined communities with stable dual-national identities. The formation of such an identity has prerequisites; such as the knowledge and understanding of the two national cultures involved, clear and sufficient communication, the preservation of the diaspora's own history, and the sustaining of various forms of collective existence, all of which will legitimise a diaspora's aspiration for recognition

Entropic measure of directional emissions in microcavity lasers

We propose a noble notion of the directional emission in microcavity lasers. First, Shannon entropy of the far-field profiles in the polar coordinate can quantify the degree of unidirectionality of the emission, while previous notions about the unidirectionality can not efficiently measure in the robust range against a variation of the deformation parameter. Second, a divergence angle of the directional emission is defined phenomenologically in terms of full width at half maximum, and it is barely applicable to a complicated peak structure. However, Shannon entropy of semi-marginal probability of the far-field profiles in the cartesian coordinate can present equivalent results, and moreover it is applicable to even the cases with a complicated peak structure of the emission