Acyclic edge coloring of graphs

An {\em acyclic edge coloring} of a graph $G$ is a proper edge coloring such that the subgraph induced by any two color classes is a linear forest (an acyclic graph with maximum degree at most two). The {\em acyclic chromatic index} \chiup_{a}'(G) of a graph $G$ is the least number of colors needed in an acyclic edge coloring of $G$. Fiam\v{c}\'{i}k (1978) conjectured that \chiup_{a}'(G) \leq \Delta(G) + 2, where $\Delta(G)$ is the maximum degree of $G$. This conjecture is well known as Acyclic Edge Coloring Conjecture (AECC). A graph $G$ with maximum degree at most $\kappa$ is {\em $\kappa$-deletion-minimal} if \chiup_{a}'(G) > \kappa and \chiup_{a}'(H) \leq \kappa for every proper subgraph $H$ of $G$. The purpose of this paper is to provide many structural lemmas on $\kappa$-deletion-minimal graphs. By using the structural lemmas, we firstly prove that AECC is true for the graphs with maximum average degree less than four (\autoref{NMAD4}). We secondly prove that AECC is true for the planar graphs without triangles adjacent to cycles of length at most four, with an additional condition that every $5$-cycle has at most three edges contained in triangles (\autoref{NoAdjacent}), from which we can conclude some known results as corollaries. We thirdly prove that every planar graph $G$ without intersecting triangles satisfies \chiup_{a}'(G) \leq \Delta(G) + 3 (\autoref{NoIntersect}). Finally, we consider one extreme case and prove it: if $G$ is a graph with $\Delta(G) \geq 3$ and all the $3^{+}$-vertices are independent, then \chiup_{a}'(G) = \Delta(G). We hope the structural lemmas will shed some light on the acyclic edge coloring problems.Comment: 19 page

Doctor of Philosophy

dissertationExplosives and drugs cause problems in society when used inappropriately. It is highly desired to detect these chemicals in a quick and reliable way with low cost. Vapor detection of explosives and drugs has been proven to be one of the most effective, practical, and noninvasive methods. Among all the methods developed so far, highly sensitive carbon nanotube-based (CNT-based) chemiresistive sensors remain promising. In this dissertation, we explored and developed three CNT-based sensors for the explosive and drug detection. In this dissertation, we proposed that the dominant mechanism of our oligomer-coated CNT-based sensors is due to the swelling of the oligomers. Based on this swelling mechanism, we have designed three oligomers or polymers functionalized CNT-based sensors for the detection of nitro-explosives, alkanes (related with ammonium nitrate/fuel oil), and amines (related with methamphetamine), respectively. Beyond the high sensitivity to the target analytes, the selectivity of the sensors was largely enhanced by the careful selection of oligomers and polymers. The three oligomers and polymers under investigation can enhance the interaction between the sensor and the analyte, and facilitate the dispersion of CNTs in a solution. For the detection of nitro-explosives, we chose an oligomer that had been successfully demonstrated as a fluorescence-based nitro-explosive sensing materials. For the detection of alkanes and amines, we introduced the alkane side chains and carboxylic acid functional groups in the polymer. This dissertation demonstrated three examples of oligomer or polymer functionalization CNT-based sensors for the detection of explosives and drugs. Meanwhile, the dominant mechanism of the sensors was proposed. This research paved ways for developing chemical vapor sensors with better sensitivity and selectivity in the future

A Data Collecting Strategy for Farmland WSNs using a Mobile Sink

To the characteristics of large number of sensor nodes, wide area and unbalanced energy consumption in farmland Wireless Sensor Networks, an efficient data collection strategy (GCMS) based on grid clustering and a mobile sink is proposed. Firstly, cluster is divided based on virtual grid, and the cluster head is selected by considering node position and residual energy. Then, an optimal mobile path and residence time allocation mechanism for mobile sink are proposed. Finally, GCMS is simulated and compared with LEACH and GRDG. Simulation results show that GCMS can significantly prolong the network lifetime and increase the amount of data collection, especially suitable for large-scale farmland Wireless Sensor Networks

Design and analysis of ultra-wide band and millimeter-wave antennas

Ph.DDOCTOR OF PHILOSOPH

The influence of cultural orientation on the entrepreneurial motivation of Chinese female returnee entrepreneurs—From the perspective of cultural integration

With the rapid development of China's economy, entrepreneurship plays an important role in advancing social and economic development. Along with the wave of global entrepreneurship, female entrepreneurs and entrepreneurial activities in China have thrived. Further more, cultural orientation can shape entrepreneurs' entrepreneurial motivation, thereby creating different types of enterprises. Based on the self-construction theory, this paper is devoted to the analysis of the influence of cultural orientation, cultural integration on female returnee entrepreneurs' entrepreneurial motivation. A total of 488 Chinese female returnee entrepreneurs participated in the survey. The structural equation modeling (SEM) and multi-group analysis were used to evaluate the relationship between the model structures. It provides a new perspective on the relationship between female returnee entrepreneurs' cultural orientation, entrepreneurial motivation, and the role of cultural integration. The results show that due to the influence of globalization and diversified cultural background, the cultural orientation of Chinese female returnee entrepreneurs tends to be more feminine rather than traditional masculine, and they pay more attention to meeting the entrepreneurial motivation of opportunity, such as interests, self-value expression and market opportunities, rather than simple survival. Cultural orientation has a significant influence on the entrepreneurial motivation of Chinese female entrepreneurs, and cultural integration plays a moderating role in this influence. The last part of the paper summarizes the theoretical and practical significance

The influence of visual marketing on consumers' purchase intention of fast fashion brands in China–An exploration based on fsQCA method

Under the rapid development of e-commerce, offline brick-and-mortar stores have been severely impacted. However, the importance of the visual, sensory and even psychological experience in the apparel industry makes offline stores still irreplaceable. The impact on consumers' visual experience cannot be ignored and is a significant influencing factor in determining consumers' psychological change and purchase intention. Especially for fast fashion brands which pursue low costs, visual marketing strategies is a cost-effective marketing tool to enhance the visual experience. In this paper, by adapting SOR theory and using fuzzy set qualitative comparative analysis (fsQCA) research method, 15 fast fashion apparel brands and 374 valid questionnaires are adapted in China to explore not only the influence of individual dimensions in visual marketing on consumers' purchase intention, but also the action of multi-dimensional combinations. The research finds that: (1) there are two driving paths for high consumers' purchase intention. The first path is a combination of high clarity of arrangement and low display density; the second path is a combination of low light intensity, high clarity of arrangement, high tonal harmony and high window appeal. (2) There are also two paths that drive non-high consumers' purchase intentions, and they are asymmetrically related to the paths that drive high consumers' purchase intentions. The findings of this study help to provide direction and suggestions for offline visual marketing strategies of fast fashion apparel brands to increase consumers' psychological perception and purchase intention through a range of visual presentation techniques

Effect of mangrove restoration on crab burrow density in Luoyangjiang Estuary, China

Background Mangrove restoration seeks to restore or rebuild degraded mangrove systems. The methods of mangrove restoration include ecological projects and restoration-oriented technologies, the latter of which are designed to restore the structure, processes as well as related physical, chemical and biological characteristics of wetlands and to ensure the provision of ecosystem services. As important components of mangrove ecosystem, benthic organisms and crabs play a key role in nutrient cycling. In addition, mangrove restoration, such as vegetation restoration measures, can lead to changes in the benthic faunal communities. This study investigates whether the presence of different mangrove species, age and canopy cover of mangrove communities affect the density of crab burrows. Methods The Luoyangjiang Estuary, in the southeast of Fujian Province, was selected as our research area. A survey, covering 14 sites, was conducted to investigate the impacts of mangrove restoration on the density of crab burrows in four rehabilitated forests with different stand ages and canopy. Results It was found that differences in vegetation types had a large impact on crab density and that the density of crab burrows was lower on exposed beaches (non-mangrove) than under mature Kandelia candel, Aegiceras corniculatum and Avicennia marina communities. In general, the amount of leaf litter and debris on mangrove mudflats was greater than on the beaches as food sources for crabs. Two-factor analysis of variance (ANOVA) shows that changes in mangrove species and age since restoration had different effects on crab burrow density. The effect of canopy cover was highly significant on crab burrow density. Conclusions The results suggest that in the process of mangrove restoration the combined effects of mangrove stand age, canopy cover and other factors should be taken into account. This study further supports the findings of the future scientific research and practice on mangrove restoration and management measures

Simple One-Pot Synthesis of Hexagonal ZnO Nanoplates as Anode Material for Lithium-Ion Batteries

Hexagonal ZnO nanoplates were synthesized via simple one-pot hydrothermal reaction of Zn(CH3COO)2 and CO(NH2)2. XRD, SEM, and HRTEM were used to investigate the composition and microstructure of the material. Together with the facile strain relaxation during structure and volume change upon cycling, this plate-like structure of ZnO is favorable for physical and chemical interactions with lithium ions because of its large contact area with the electrolyte, providing more active sites and short diffusion distances. The resulting hexagonal ZnO nanoplates electrode exhibited good cyclability and delivered a reversible discharge capacity of 368 mAh g−1 after 100 cycles at 0.1 C

Ultrastructure of telocytes, a new type of interstitial cells in the myocardium of the Chinese giant salamander (Andrias davidianus)

Telocytes (TCs) are new interstitial cells, and they are involved in tissue regeneration, particularly in heart. Therefore, TCs are suggested to be a promising cell in regenerative medicine. However, the information of location structural characteristics and functions of TCs is still limited. In this study, cardiac TCs of the Chinese giant salamanders (Andrias davidianus) were identified by transmission electron microscopy. TCs were located in the interstitium between cardiomyocytes (CM). TCs possessed distinctive ultrastructural characteristics, including one to two very long and thin moniliform telopodes (Tps), emerging points from the cell body, caveolae, dichotomous branchings, labyrinthic systems, neighbouring exosomes and homo-cellular contacts between Tps. TCs/Tps were frequently observed in close proximity to cardiomyocytes. Moreover, Tps established hetero-cellular contacts with cardiomyocytes. Our results confirm the presence of TCs in the myocardium of the A. davidianus. This will help us to better understand roles of TCs in amphibian hearts

A facile direct route to N-(un)substituted lactams by cycloamination of oxocarboxylic acids without external hydrogen

Lactams are privileged in bioactive natural products and pharmaceutical agents and widely featured in functional materials. This study presents a novel versatile approach to the direct synthesis of lactams from oxocarboxylic acids without catalyst or external hydrogen. The method involves the in situ release of formic acid from formamides induced by water to facilitate efficient cycloamination. Water also suppresses the formation of byproducts. This unconventional pathway is elucidated by a combination of model experiments and density functional theory calculations, whereby cyclic imines (5‐methyl‐3,4‐dihydro‐2‐pyrrolone and its tautomeric structures) are found to be favorable intermediates toward lactam formation, in contrast to the conventional approach encompassing cascade reductive amination and cyclization. This sustainable and simple protocol is broadly applicable for the efficient production of various N‐unsubstituted and N‐substituted lactams