Revising Concept of Resonant Cycle Length and Investigation of Resonant Signal Timing Plans

The most difficult part of designing optimal traffic signal timings is selection of an appropriate cycle length. In recent years, a new concept called “resonant cycle” has been introduced by several researchers referring to a particular cycle length that provides good performance on two-way arterial streets for a wide range of traffic flows. However, an attempt to define a resonant cycle length is a difficult task on its own as it has ambiguous connotation and inconsistent meaning to various scholars. Two major schools of thought are: resonant cycles serve either to provide good progression only for coordinated movements or they provide good conditions for all movements (equally prioritizing traffic on main street and side street). This research addresses inconsistencies in definitions and ambiguity of the meaning of resonant cycle length by introducing a new concept called Resonant Signal Timing Plan (RSTP) that , besides cycle length, considers that the entire set of signal timings (splits, offsets, etc.) needs to be “resonant”, or work well with a range of traffic volumes. To investigate the existence of such an RSTP, a methodology was developed to test a number of signal timing optimization scenarios. Each of the tested signal timing plans was evaluated on overall network level (all movements) and main-corridor level (coordinated movements only). The results of evaluations on network level reveal no existence of the RSTP; each candidate RSTP could provide decent performance only for a few hours of similar traffic demands. Similarly, the corridor-level evaluation did not find any RSTP either as conditions differ significantly for traffic in inbound and outbound directions

Flexible Multi-Group Single-Carrier Modulation: Optimal Subcarrier Grouping and Rate Maximization

Orthogonal frequency division multiplexing (OFDM) and single-carrier frequency domain equalization (SC-FDE) are two commonly adopted modulation schemes for frequency-selective channels. Compared to SC-FDE, OFDM generally achieves higher data rate, but at the cost of higher transmit signal peak-to-average power ratio (PAPR) that leads to lower power amplifier efficiency. This paper proposes a new modulation scheme, called flexible multi-group single-carrier (FMG-SC), which encapsulates both OFDM and SC-FDE as special cases, thus achieving more flexible rate-PAPR trade-offs between them. Specifically, a set of frequency subcarriers are flexibly divided into orthogonal groups based on their channel gains, and SC-FDE is applied over each of the groups to send different data streams in parallel. We aim to maximize the achievable sum-rate of all groups by optimizing the subcarrier-group mapping. We propose two low-complexity subcarrier grouping methods and show via simulation that they perform very close to the optimal grouping by exhaustive search. Simulation results also show the effectiveness of the proposed FMG-SC modulation scheme with optimized subcarrier grouping in improving the rate-PAPR trade-off over conventional OFDM and SC-FDE.Comment: Submitted for possible conference publicatio

Microscopic Particle Manipulation via Optoelectronic Devices

The optoelectronic tweezers (or optically induced dielectrophoresis (DEP)) have showed the ability to parallelly position a large number of colloidal microparticles without any template. The microparticles can be trapped and driven by the dielectrophoretic forces induced by the optical micropatterns in OET devices. In this chapter, the design and fabrication of flat optoelectronic devices (FOD) and hybrid optoelectronic device (HOD) are described. In the typical FOD, the manipulation modes including filtering, transporting, concentrating and focusing controlling regimes are experimentally demonstrated and analyzed. The controllable rotation of self-assembled microparticle chains in FOD has also been investigated, and a method incorporating the optically induced electrorotation (OER) and AC electroosmotic (ACEO) effects is numerically and experimentally implemented for manipulating microparticle chains. Based on the above research of FOD, a hybrid DEP microdevice HOD is conceptually and experimentally proposed. The HOD integrates with metallic microelectrode layer and the underneath photoconductive layer with projected optical virtual electrodes. FOD and HOD hybrid device enables the active driving, large-scale patterning and local position adjustment of microparticles. These techniques make up the shortcoming of low flexibility of traditional metallic microelectrodes and integrate the merits of both the metal electrode-induced and microimage-induced DEP techniques

Designer's Choice for Paid Research Study

We consider constrained sampling problems in paid research studies or clinical trials. When qualified volunteers are more than the budget allowed, we recommend a D-optimal sampling strategy based on the optimal design theory and develop a constrained lift-one algorithm to find the optimal allocation. We theoretically justify the optimality of our sampling strategy and show by simulations and a real data example its advantage over simple random sampling and proportionally stratified sampling.Comment: 22 page