Scattering investigation based on acoustical holography

The objective of this research is to investigate sound scattering by an object using a two-surface measurement technique that separates the incident field and the scattered field. The separation technique is developed in cartesian and cylindrical coordinates. The decomposition method in the cartesian coordinate system is based on the principle that any wave form can be decomposed into plane-wave components by using a two dimensional spatial Fourier transform. For the cylindrical coordinate system, a two plane separation technique is based on decomposing the sound field into cylindrical waves. Numerical simulations are performed and the effect of various parameters are investigated. Specifically, the distance between two measurement surfaces, the distance between measurement points, and the aperture size are investigated. In addition, experimental studies were conducted inside an anechoic chamber with a baffled loudspeaker as a source, illuminating four different scatterers. The decomposed scattered field is then used to estimate the far-field target strength. The experiments demonstrate the feasibility of the field separation technique

Exploring semi-solid alloy deformation with discrete element method simulations and synchrotron radiography

Semi-solid alloys are deformed in a wide range of pressurised casting processes; an improved understanding and modelling capability are required to minimise defect formation and optimise productivity. This thesis combines thin-sample in-situ X-ray radiography of semisolid Al-Cu alloy deformation with 2D coupled lattice Boltzmann method – discrete element method (LBM-DEM) simulations. Mechanisms of strain heterogeneity and localisation are identified during semi-solid deformation in globular Al-Cu alloys with various combinations of initial solid fraction and strain rates. The calibrated set of LBM-DEM simulations is then used to obtain information that is not available in X-ray imaging to extract deeper insights into the semi-solid deformation behaviours observed in the experiments. It is found that the local contraction and dilation of the percolating grain assembly are highly influenced by the initial solid fraction. When deforming a low solid fraction alloy, macroscopic contraction due to grains being pushed together increases the local liquid pressure and expels liquid from the sample surface. In contrast, deforming high solid fraction alloys leads to macroscopic shear-induced dilation by grains pushing each other apart and surface menisci are sucked-in due to the decrease in interstitial liquid pressure. It is also shown that the macroscopic behaviour of semi-solid alloy deformation undergoes a range of rheological transitions with increasing solid fraction. First from a suspension to a percolating solid network and, later, from net dilation to shear cracking. These transitions are investigated with LBM-DEM simulations, and the transition to shear cracking is shown to be related to the local decrease in interstitial liquid pressure caused by shear-induced dilation. The verified coupled LBM-DEM simulation is shown to exhibit a load:deformation response consistent with the critical state framework of soil mechanics, indicating that this approach can be useful for modelling thermomechanics in casting processes.Open Acces

Technology Advantage and Trade: Home Market Effects Revisited

According to conventional home market effects, free trade tends to shrink the market share for the smaller economy in the differentiated manufacturing goods, and in the extreme, leads to a complete hollowing out of the industry. In departing from the original Helpman-Krugman modeling assumptions behind the home market effects, we introduce technology differences between trading partners and prove that the home market effects will be offset and will even reverse if the small economy has better technology than the other country. We also prove that even with identical country size, the intra-industry trade addressed in the existing literature may not occur; it will occur only if the technology differential lies within a certain range that is positively affected by the level of transport cost.Home market Effects, Country Size, Technology Differential

On the DP/NP Analysis of Mandarin Chinese and its Implications

In this paper, I examine the nominal structure in Mandarin Chinese (MC). Specifically, I discuss the issue of whether the DP projection is always present in syntax (the Universal DP Hypothesis) or the existence of DP may be dependent on languages (the DP/NP Parameter). Based on a test established in Despić (2009), I examine the relevant data in MC and argue that, contrary to the claim traditionally held in the literature, DP does not exist in MC. Using tests from binding paradigm, it is further shown that classifiers do head their own projections in MC, as previously argued in the literature. Similar examination is also applied to Japanese to show that Japanese behaves alike with MC in two respects. First, DP does not exist in Japanese, either. Second, classifiers are also heading their projection, not merely adjoined to NPs. Lastly, as a result of the paradigm, I discuss some of the consequences on the nature of classifiers and argue that, while classifiers in MC and Japanese are enclitics and need a preceding host, classifiers in Cantonese are free morphemes and can occur alone by themselves

Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges

With the rapid development of marine activities, there has been an increasing number of maritime mobile terminals, as well as a growing demand for high-speed and ultra-reliable maritime communications to keep them connected. Traditionally, the maritime Internet of Things (IoT) is enabled by maritime satellites. However, satellites are seriously restricted by their high latency and relatively low data rate. As an alternative, shore & island-based base stations (BSs) can be built to extend the coverage of terrestrial networks using fourth-generation (4G), fifth-generation (5G), and beyond 5G services. Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs. Despite of all these approaches, there are still open issues for an efficient maritime communication network (MCN). For example, due to the complicated electromagnetic propagation environment, the limited geometrically available BS sites, and rigorous service demands from mission-critical applications, conventional communication and networking theories and methods should be tailored for maritime scenarios. Towards this end, we provide a survey on the demand for maritime communications, the state-of-the-art MCNs, and key technologies for enhancing transmission efficiency, extending network coverage, and provisioning maritime-specific services. Future challenges in developing an environment-aware, service-driven, and integrated satellite-air-ground MCN to be smart enough to utilize external auxiliary information, e.g., sea state and atmosphere conditions, are also discussed

タイショウ キュウネン タイワン チホウ セイド ノ セイリツ カテイ 1 タイワン ソウトクフ 二 オケル チホウ セイド カイカク ジギョウ ヲ チュウシンニ

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Society Exchange Characteristics, Service Quality, and Relationship Quality between Hospital and Its Suppliers

Successful supply chain management provides an enterprise with a new competitive advantage. However, successful supply chain performance is based on a high level of trust and strong commitment among supply chain partners. Studies have indicated that communication, partner’s reputation, perceived benefits, fairness, and relationship tenure that are within the context of social exchange theory have an effect on trust. In the current study, we attempted to integrate two types of theories of social exchange and service quality by proposing an integrated model that influences the factor to trust and commitment. We then applied structural equation modeling to test the model. The study results indicated that a hospital’s trust in its supply chain partner is highly associated with commitment. The study included respondents comprising medical device procurement staff working in hospitals within Taiwan. A total of 500 questionnaires were distributed; 316 completed questionnaires were received. The results revealed that communication, partner’s reputation, and perceived benefits had a positive effect on trust. Service quality was also determined to have a positive effect on trust and commitment. This result should provide reference for a hospital and its relationship with suppliers, which helps monitor decision variables in the supply chain management of medical devices

タイショウ キュウネン タイワン チホウ セイド ノ セイリツ カテイ 2 カン タイワン ソウトクフ 二 オケル チホウ セイド カイカク ジギョウ ヲ チュウシンニ

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