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Circular cylinders in cross-flow have been extensively studied in the last century. However, there are still many unsolved problems in this area, one of which is the flow structure around two staggered finite circular cylinders. This thesis mainly focuses on an experimental investigation of the vortex shedding characteristics of two staggered finite circular cylinders of equal diameter in cross-flow. Wind tunnel experiments were conducted to measure the vortex shedding frequency at the mid-height of the two cylinders and along the height of the two cylinders. Two identical circular cylinders of aspect ratio AR = 9 were partially immersed in a flat-plate turbulent boundary layer, where the boundary layer thickness to cylinder height ratio at the location of the cylinders was δ/H = 0.4. The Reynolds number based on the cylinder diameter was Re<i>D</i> = 2.4z_x~104. Centre-to-centre pitch ratios of <i>P/D</i> = 1.125, 1.25, 1.5, 2, 2.5, 3, 4 and 5 were examined and the incidence angle was incremented in small steps from á = 0° to 180°. For each configuration of the cylinders, the vortex shedding frequency, represented in dimensionless form as the Strouhal number, St, was measured with a single-component hot-wire anemometer. Also, a seven-hole pressure probe was used to measure the time-averaged wake velocity field behind the cylinders at selected configurations in order to get a better understanding of the wake structure.<p>The vortex shedding frequencies measured at the mid-height of the cylinders clearly showed the similarities and differences of vortex shedding between two staggered finite and infinite circular cylinders. The Strouhal number behavior of the two finite circular cylinders is generally similar to that of two infinite circular cylinders, but the values of St for the two finite cylinders were found for most cases to be smaller than the case of the infinite cylinders.<p>The measurements of vortex shedding frequency along the heights of each finite cylinder revealed that, for most incidence angles, the value of the Strouhal number remains constant along the height of the cylinder, but a notable variation in the shape and strength of the vortex shedding peak along the heights of the cylinders is observed. Sharp and strong peaks in the power spectra are measured around the mid-height of the cylinder. Broader and weaker peaks are found both at the base of the cylinder and near the free end. At several particular configurations, the vortex shedding frequency changes along the height of the cylinder, caused by the varying flow pattern in the vertical direction.<p>Wake measurements showed the velocity field behind the two finite circular cylinders arranged in tandem configurations of P/D = 1.125, 2 and 5. The experimental data revealed that the flow structure behind two finite circular cylinders arranged in a tandem configuration is much more complicated than that of the single finite circular cylinder. The downwash flow from the tip of the downstream cylinder is weaker due to the flow interaction between the free ends of two cylinders, and this downwash flow becomes stronger with increasing P/D. A similar trend happens to the vorticity of the tip vortex structures. However, the upwash flow behind the downstream cylinder is not strongly affected by the existence of the upstream cylinder.

Circular cylinders in cross-flow have been extensively studied in the last century. However, there are still many unsolved problems in this area, one of which is the flow structure around two staggered finite circular cylinders. This thesis mainly focuses on an experimental investigation of the vortex shedding characteristics of two staggered finite circular cylinders of equal diameter in cross-flow. Wind tunnel experiments were conducted to measure the vortex shedding frequency at the mid-height of the two cylinders and along the height of the two cylinders. Two identical circular cylinders of aspect ratio AR = 9 were partially immersed in a flat-plate turbulent boundary layer, where the boundary layer thickness to cylinder height ratio at the location of the cylinders was δ/H = 0.4. The Reynolds number based on the cylinder diameter was Re<i>D</i> = 2.4z_x~104. Centre-to-centre pitch ratios of <i>P/D</i> = 1.125, 1.25, 1.5, 2, 2.5, 3, 4 and 5 were examined and the incidence angle was incremented in small steps from á = 0° to 180°. For each configuration of the cylinders, the vortex shedding frequency, represented in dimensionless form as the Strouhal number, St, was measured with a single-component hot-wire anemometer. Also, a seven-hole pressure probe was used to measure the time-averaged wake velocity field behind the cylinders at selected configurations in order to get a better understanding of the wake structure.<p>The vortex shedding frequencies measured at the mid-height of the cylinders clearly showed the similarities and differences of vortex shedding between two staggered finite and infinite circular cylinders. The Strouhal number behavior of the two finite circular cylinders is generally similar to that of two infinite circular cylinders, but the values of St for the two finite cylinders were found for most cases to be smaller than the case of the infinite cylinders.<p>The measurements of vortex shedding frequency along the heights of each finite cylinder revealed that, for most incidence angles, the value of the Strouhal number remains constant along the height of the cylinder, but a notable variation in the shape and strength of the vortex shedding peak along the heights of the cylinders is observed. Sharp and strong peaks in the power spectra are measured around the mid-height of the cylinder. Broader and weaker peaks are found both at the base of the cylinder and near the free end. At several particular configurations, the vortex shedding frequency changes along the height of the cylinder, caused by the varying flow pattern in the vertical direction.<p>Wake measurements showed the velocity field behind the two finite circular cylinders arranged in tandem configurations of P/D = 1.125, 2 and 5. The experimental data revealed that the flow structure behind two finite circular cylinders arranged in a tandem configuration is much more complicated than that of the single finite circular cylinder. The downwash flow from the tip of the downstream cylinder is weaker due to the flow interaction between the free ends of two cylinders, and this downwash flow becomes stronger with increasing P/D. A similar trend happens to the vorticity of the tip vortex structures. However, the upwash flow behind the downstream cylinder is not strongly affected by the existence of the upstream cylinder.

Suppose G is a graph and p >= 2q are positive integers. A color-list is a mapping L: V --> P(0, 1,...,p-1) which assigns to each vertex a set L(v) of permissible colors. An L-(p, q)-coloring of G is a (p, q)-coloring h of G such that for each vertex v, h(v) in L(v). We say G is L-(p, q)-colorable if such a coloring exists. A color-size-list is a mapping f: V -->{0, 1, 2,..., p}, which assigns to each vertex v a non-negative integer f(v). We say G is f-(p, q)-colorable if for every color-list L with |{L}(v)| = f(v), G is L-(p, q)-colorable. For odd cycles C, Raspaud and Zhu gave a sharp sufficient condition for a color-size-list f under which C is f-(2k+1, k)-colorable. The corresponding question for even cycles remained open. In this paper, we consider list circular coloring of even cycles. For each even cycle C of length n and for each positive integer k, we give a condition on f which is sufficient and sharp for C to be f-(2k+1, k)-colorable.

Suppose $G$ is a graph and $e=ab$ is an edge of $G$. For a positive integer $k$, the $G$-necklace of length $k$ (with respect to edge $e$), denoted by $N_k(G)$, is the graph constructed as follows: Take the vertex disjoint union of $k$ copies of $G$, say $Q_1 cup Q_2 cup cdots cup Q_k$, where each $Q_i$ is a copy of $G$, with $e_i=a_ib_i$ be the copy of $e=a b$ in $Q_i$. Add a vertex $u$, delete the edges $e_i$ for $i=1, 2, cdots, k$ and add edges: $ua_1, b_1a_2, b_2a_3, cdots, b_{k-1}a_k, b_ku$. This thesis determines the circular chromatic indexes of $G$-necklaces for $G = K_{2n}$ and $G= K_{m, m}$.(¨£¹q¤l½×¤å²Ä¤»­¶)

In this thesis, we propose tag and reader antennas which are suitable when attended to metal material for Radio Frequency Identification (RFID) systems. For tag antenna design, we use microstrip antenna with ground plane to reduce the metal effect. In order to match the impedance of different IC chip, some parameter of the tag antenna are designed and described, which can be used to adjust the impedance of tag antenna. For reader antenna design, circularly polarized patch antenna can be achieved by using dual-feeding technique with U-shaped aperture-coupled, where the dual feeds with a phase shift and equal input power amplitude are provided by a Wilkinson power divider. Therefore, a good right-hand circular polarization is obtained and a 3-dB CP bandwidth of the designed reader antenna is greater than 30 ¢H. 900 We then design dual-band antenna and broad CP bandwidth antennas. In the dual-band design, two resonant paths are utilized to cover 915 and 2450 MHz bands that can be used for RFID systems in UHF and ISM bands. In the broad CP bandwidth design, a square slot antenna is used with a cross patch placed at the center of the square slot. Two orthogonal resonant modes with phase difference and equal input power amplitude can be excited by choosing the proper dimensions of the cross patch. A 3-dB CP bandwidth of the designed circularly polarized antenna is greater than 12¢H.

Inaug.-Diss.--Basel. / Bibliography: p. 136-137.

Inaug.-Diss.--Basel. / Bibliography: p. 136-137.

This thesis reports on research undertaken to investigate the implementation of a Circular approach within the leather industry, through the definition of a framework and development of an economic decision-making support tool. The core objective of the research is to identify the underpinning opportunities and challenges involved in creating recycling solutions for leather waste. The research contributions can be considered in four key areas. The first part of the thesis consists of a review of the use of leather across industry sectors and the existing waste management and recycling systems for leather waste. On consideration of this review it clearly shows a lack of systematic thinking around the creation and optimisation of recovery systems for leather waste. This review concludes that there is significant room for improvement of the current waste management and recycling solutions for leather waste. A variety of value-added products can be recovered from these wastes but only if the leather can be successfully separated from the other materials (such as rubbers and polymers) within end-of-life products and manufacturing wastes. The second part of the research defines a framework for implementing a Circular approach within the leather industry. This framework supports mapping and characterisation of the leather waste stream and the design of recycling and processing strategies for leather waste. The third part of the research is concerned with the development of a decision-support tool for the economic viability of leather recycling systems. The support tool considers all cost factors and combines them to give a single factor upon which the economic effectiveness of different leather recycling scenarios can be evaluated. Finally, the validity of the framework for leather waste recycling is assessed through the completion of two case studies. These case studies demonstrate the flexibility of the framework in supporting both horizontal (across lifecycle) leather recycling and vertical (across industry sector) leather recycling. In summary, the research clearly highlights the need for systematic thinking and flexible strategies when creating leather recycling systems. Failure to incorporate flexibility into future recycling systems puts the recycling industries at risk of being unable to effectively manage future waste streams. Conversely, early consideration and incorporation of flexible processing strategies into recycling systems could enable the recovery of high-quality recycled materials that support a circular approach to manufacturing and resource use.

As emerging chiral metamaterials, plasmonic nanospirals (NSs) show strong optical activity that is expected to enhance the enantiodiscrimination of chiral molecules or help in the design of a new generation of integrated optical devices. The study of the optical activity of plasmonic NSs is still in its infancy, and no analytical model exists to describe their chiroptical mechanism. In this study, numerical and analytical simulations are devised to investigate the optical activity of plasmonic NSs that are generated by glancing-angle deposition. The findings will pave the way for the development of novel optical and optoelectronic devices with integrated functions. The CD spectrum of a closely packed random AgNS array has two CD peaks in the UV and visible regions with opposite signs. The pitch-normalized CD in the UV regime tends to be independent of the helical pitch, but that in the visible regime decreases in amplitude as helical pitch increases. The difference can be explained using an analytical LC circuit model and finite-element method simulation. The LC circuit model is used to quantitatively evaluate the chiroptical contribution. It is revealed that radiative loss makes an important chiroptical contribution to the two CD modes and that the visible CD mode receives a greater contribution from radiative loss than does the UV CD mode. Finally, the heterochiral biaxial AgNS arrays alter the sign of the visible CD by switching the incident direction, which shows that the arrays can function as circular polarizers in the visible regime. Furthermore, when AgNSs are deposited on a polymer substrate coated with indium tin oxide, the chiroptical flexible thin film has excellent chiroptical stability when exposed to forward mechanical bending, paving the way for the development of flexible or wearable chiroplasmonic devices.