We report a comparison of different capping materials on the intermixing of modulation p-doped InAs/In(Ga)As quantum dots (QD). QD materials with different caps are shown to exhibit significant difference in their optical properties during the annealing process. The selective area intermixing technique is demonstrated to laterally integrate two and three different QD light emitting devices with a single electrical contact. A spectral bandwidth of 240nm centered at 1188nm is achieved in a device with two sections. By calculating the point spread function for the obtained emission spectra, and applying the Rayleigh criteria for resolution, an axial resolution of 3.5μm is deduced. A three section device realizes a spectral bandwidth of 310nm centered at 1145nm. This corresponds to an axial resolution of 2.4μm. Such a small predicted axial resolution is highly desirable in optical coherence tomography system and other coherence-based systems applications.

a b s t r a c tSelective laser sintering (SLS) enables the fast, flexible and cost-efficient production of parts directly from 3D CAD data. Unlike more established machine tools, there is a marked lack of process monitoring and feedback control of key process variables. In-situ analysis techniques permit the emergence of repair techniques, in-process optimization of production parameters, and will also serve to save time and material. In this study, optical coherence tomography (OCT) is used for the first time to evaluate components produced by SLS. Using a Polyamide-PA2200, surface defects are analyzed and the limiting factors associated with the measurement technique are quantified. OCT is shown to be a useful technique for evaluating surface irregularities alongside sub-surface defects that have resulted from poor sintering or non-homogeneous powder spreading. We demonstrate detection and quantification of surface defects such as cracks, pores and voids on a~30 μm scale. Furthermore, we show that this technique can resolve 'built-in' fine features within a 200 to 400 μm depth below the surface, covering typical layer thicknesses used by this process. This capability paves the way for real-time monitoring of the SLS process for assurance, or even dynamic correction of defects during the build.

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The volume of passenger flow in urban rail transit network operation continues to increase. Effective measures of passenger flow control can greatly alleviate the pressure of transportation and ensure the safe operation of urban rail transit systems. The controllability of an urban rail transit passenger flow network determines the equilibrium state of passenger flow density in time and space. First, a passenger flow network model of urban rail transit and an evaluation index of the alternative set of flow control stations are proposed. Then, the controllable determination model of the urban rail transit passenger flow network is formed by converting the passenger flow distribution into a system state equation based on system control theory. The optimization method of passenger flow control stations is established via driver node matching to realize the optimized control of network stations. Finally, a real-world case study of the Beijing subway network is presented to demonstrate that the passenger flow network is controllable when driver nodes compose 25.3% of the entire network. The optimization of the flow control station, set during the morning peak, proves the efficiency and validity of the proposed model and algorithm.