ECONOMIC APPROACHES AND MARKET STRUCTURES FOR TEMPORAL-SPATIAL SPECTRUM SHARING

In wireless communication systems, economic approaches can be applied to spectrum sharing and enhance spectrum utilization. In this research, we develop a model where geographic information, including licensed areas of primary users (PUs) and locations of secondary users (SUs), plays an important role in the spectrum sharing system. We consider a multi-price policy and the pricing power of noncooperative PUs in multiple geographic areas. Meanwhile, the value assessment of a channel is price-related and the demand from the SUs is price-elastic. By applying an evolutionary procedure, we prove the existence and uniqueness of the optimal payoff for each PU selling channels without reserve. In the scenario of selling channels with reserve, we predict the channel prices for the PUs leading to the optimal supplies of the PUs and hence the optimal payoffs. To increase spectrum utilization, the scenario of spatial spectrum reuse is considered. We consider maximizing social welfare via on-demand channel allocation, which describes the overall satisfaction of the SUs when we involve the supply and demand relationship. We design a receiver-centric spectrum reuse mechanism, in which the optimal channel allocation that maximizes social welfare can be achieved by the Vickrey-Clarke-Groves (VCG) auction for maximal independent groups (MIGs). We prove that truthful bidding is the optimal strategy for the SUs, even though the SUs do not participate in the VCG auction for MIGs directly. Therefore, the MIGs are bidding truthfully and the requirement for social welfare maximization is satisfied. To further improve user satisfaction, user characteristics that enable heterogeneous channel valuations need to be considered in spatial spectrum reuse. We design a channel transaction mechanism for non-symmetric networks and maximize user satisfaction in consideration of multi-level flexible channel valuations of the SUs. Specifically, we introduce a constrained VCG auction. To facilitate the bid formation, we transform the constrained VCG auction to a step-by-step decision process. Meanwhile, the SUs in a coalition play a coalitional game with transferable utilities. We use the Shapley value to realize fair payoff distribution among the SUs in a coalition

Numerical Study of Manifold Design for Heat Pipe Solar Collectors

This project studies an active solar water heating system which uses glass evacuated tube solar collectors. The heat pipes inside the evacuated tubes transfer the absorbed solar energy to water in the manifold through the copper headers of heat pipes. A numerical model will be developed to simulate the heat transfer and fluid flow inside the manifold under different solar radiation flux levels and fluid flow rates. The simulation results provide understanding of the heat transfer and fluid flow patterns inside the manifold and will be used to help optimize the manifold design

Construction of Clinical Biobanks and the Medical Ethics

Nowadays, various types and forms of clinical biobanks have been gradually established worldwide, which have become one of the important components and research platforms of life science and related disease researches in the medical system. This article mainly introduces the construction, management and operation of clinical biobanks, and discusses the medical ethics faced by it

On the Construction of Biobank in General Hospitals

Objective: Discussion on a series of biospecimen related issues are conducted, such as collection and preservation, quality control, as well as management and application, during the construction of human tissue biobank in a general hospital. Methods: To develop a set of standardized operational procedures and to collect tissue samples, such as whole blood, serum, plasma, fresh frozen tissues, cerebrospinal fluid, and paraffin-embedded tissues, which were classified and made aliquots according to different requirements, and stored at -80℃ temperature refrigerator or in liquid nitrogen. At the same time, a set of information management software was used to realize management of the biobank. Results: Currently, there are more than 20,000 specimens of various benign and malignant cases, which cover 380 diseases, being collected in the biological database in our hospital. These specimens include paraffin-embedded tissue, fresh frozen tissue, femoral head, whole blood, plasma, serum and cerebrospinal fluid, etc. A large number of these specimensare beneficial is used in clinical research at present. Conclusion: The establishment of biological sample bank can maximize the value of non-reborn human tissue specimens, and provide normal control standards as well as benign and malignant disease standards for clinical diagnosis and treatment, which is of great significance to the research of disease pathogenesis and the development of detection technology

Scanning tunneling microscopy study of the possible topological surface states in BiTeCl

Recently, the non-centrosymmetric bismuth tellurohalides such as BiTeCl are being studied as possible candidates of topological insulators. While some photoemission studies showed that BiTeCl is an inversion asymmetric topological insulator, others showed that it is a normal semiconductor with Rashba splitting. Meanwhile, first-principle calculationsfailed to confirm the existence of topological surface states in BiTeCl so far. Therefore, the topological nature of BiTeCl requires further investigation. Here we report low temperature scanning tunneling microscopy study on the surface states of BiTeCl single crystals. On the tellurium-terminated surfaces with low defect density, strong evidences for topological surface states are found in the quasi-particle interference patterns generated by the scattering of these states, both in the anisotropy of the scattering vectors and the fast decay of the interference near step edges. Meanwhile, on samples with much higher defect densities, we observed surface states that behave differently. Our results help to resolve the current controversy on the topological nature of BiTeCl.Comment: 13pages,4figure

Meta-Analysis: Contrast-Enhanced Ultrasound Versus Conventional Ultrasound for Differentiation of Benign and Malignant Breast Lesions

This meta-analysis aimed to compare the diagnostic performance of contrast-enhanced ultrasound (CEUS), conventional ultrasound (US) combined with CEUS (US + CEUS) and US for distinguishing breast lesions. From thorough literature research, studies that compared the diagnostic performance of CEUS versus US or US + CEUS versus US, using pathology results as the gold standard, were included. A total of 10 studies were included, of which 9 compared the diagnostic performance of CEUS and US, and 5 studies compared US + CEUS and US. In those comparing CEUS versus US, the pooled sensitivity was 0.93 (95% CI: 0.91–0.95) versus 0.87 (95% CI: 0.85–0.90) and pooled specificity was 0.86 (95% CI: 0.84–0.88) versus 0.72 (95% CI: 0.69–0.75). In studies comparing US + CEUS versus US, the pooled sensitivity was 0.94 (95% CI: 0.92–0.96) versus 0.87 (95% CI: 0.84–0.90) and pooled specificity was 0.86 (95% CI: 0.82–0.89) versus 0.80 (95% CI: 0.76–0.84). In terms of diagnosing breast malignancy, areas under the curve of the summary receiver operating characteristic (of both CEUS (p = 0.003) and US + CEUS (p = 0.000) were statistically higher than that of US. Both CEUS alone and US + CEUS had better diagnostic performance than US in differentiation of breast lesions, and US + CEUS also had low negative likelihood ratio