Laterally-coupled distributed feedback (LC-DFB) lasers use a lithographic fabrication step to define the distributed feedback grating, avoiding subsequent regrowth. Using higher order gratings can enhance the lithographic tolerance for lower resolution patterning, yielding lasers more amenable to fabrication. We show that LC-DFB lasers with higher order gratings, although requiring a higher threshold gain than those of first-order, provide a degree of longitudinal mode discrimination. Incorporating radiating partial waves, we have calculated modified coupled-mode coefficients for various duty cycles, grating orders, and grating geometries using a two-dimensional finite-element method. The modified coupled-mode equations were solved with and without a lambda/4 phase shift. The phase shift, while beneficial for first-order gratings, was found to generally diminish laser performance for lasers with higher order gratings.

A test method that measures the current-voltage I-V curve of a photovoltaic (PV) cell or module in real time is presented as a means of characterizing and understanding the inherently variable nature of performance under field conditions. Temperature, incident light intensity, orientation to the light source, incident spectrum, the uniformity of illumination, as well as a diverse set of failure mechanisms, both catastrophic and otherwise, have characteristic effects on the I-V curve. Seeing the I-V curve change dynamically with these influences allows visual correlation to real-time events. With a live I-V curve generated by performing forward and reversed bias sweeps repeatedly, the effect of parasitic inductance and bias sweep rate on the measurement can be demonstrated directly. This technique also ensures that the device junction is held in quasi-thermal equilibrium during the measurement. The relative alignment of optics in a concentrating photovoltaic module is analyzed to demonstrate the value of the live I-V curve.

The Energy-efficiency of demand management technologies and customer’s experience have emerged as important issues as consumers began to heavily adopt these technologies. In this context, where the electrical load imposed on the smart grid by residential users needs to be optimized, it can be better managed when customer’s comfort parameters are used, such as thermal comfort and preferred appliance usage time interval. In this paper a multi-layer architecture is proposed that uses a multi-objective optimization model at the energy consumption level to take consumer comfort and experience into consideration. The paper shows how our proposed Clustered Sequential Management (CSM) approach could improve consumer comfort via appliance use scheduling. To quantify thermal comfort, we use thermodynamic solutions for a Heating Ventilation and Air Conditioner (HVAC) system and then apply our scheduling model to find the best time slot for such thermal loads, linking consumer experience to power consumption. In addition to thermal loads, we also include non-thermal loads in the cost minimization and the enhanced consumer experience. In this hierarchal algorithm, we classified appliances by their load profile including degrees of freedom for consumer appliance prioritization. Finally, we scheduled consumption within a Time of Use (ToU) pricing model. In this model, we used Mixed Integer Linear Programming (MILP) and Linear Programming (LP) optimization for different categories with different constraints for various loads. We eliminate the customer’s inconvenience on thermal load considering ASHRAE standard, increase the satisfaction on EV optimal chagrining constrained by minimum cost and achieve the preferred usage time for the non-interruptible deferrable loads. The results show that our model is typically able to achieve cost minimization almost equal to 13% and Peak-to-Average Ratios (PAR) reduction with almost 45%.

We reveal the fundamental relation between linear photonic crystal symmetries and the local polarization states of its Bloch modes, in particular the location and nature of polarization singularities as established by rigorous group theoretic analysis, encompassing the full system symmetry. This is illustrated with the fundamental transverse electric mode of a two-dimensional hexagonal photonic crystal, in the vanishing contrast limit and at the K point. For general Wyckoff positions within the fundamental domain, the transformation of a local polarization state is determined by the nature of the symmetry operations that map to members of its crystallographic orbit. In particular, the site symmetries that correspond to specific Wyckoff positions constrain the local polarization state to singular character — circular, linear or disclination. Moreover, through the application of a local symmetry transformation relation, and the group’s character table, the precise natures of the singularities may be determined from self-consistency arguments.

Demand response (DR) has been studied widely in the smart grid literature, however, there is still a significant gap in approaches that address security, privacy, and robustness of settlement processes simultaneously. The need for security and robustness emerges as a vital property, as Internet of Things (IoT) devices become part of the smart grid; in the form of smart meters, home energy management systems (HEMSs), intelligent transformers, and so on. In this paper, we use energy blockchain to secure energy transactions among customers and the utility. In addition, we formulate a mixed-strategy stochastic game model to address uncertainties in DR contributions of agents and achieve optimal demand response decisions. This model utilizes the processing hardware of customers for block mining, stores customer DR agreements as distributed ledgers, and offers a smart contract and consensus algorithm for energy transaction validation. We use a real dataset of residential demand profiles and photovoltaic (PV) generation to validate the performance of the proposed scheme. The results show the impact of electric vehicle (EV) discharging and customer demand reduction on increasing the probability of successful block mining and improving customer profits. Moreover, the results demonstrate the security and robustness of our consensus algorithm for detecting malicious activities.

A physical realization of a random structural percolation system, formed from sintered glass microspheres, has allowed its elasticity and vibrational dynamics to be studied using ultrasonic techniques in the 1–55 MHz frequency range. Samples with occupied volume fractions φ between 0.18 and 0.64 were prepared, enabling the percolation threshold φ_c to be determined. From measurements of the ultrasonic velocity, the elasticity exponent τ was found to be 2.9±0.1, which falls midway between the best theoretical estimates for scalar and bond-bending elasticity. Very low values of Poisson's ratio were observed, and data for the longitudinal and shear wave velocities were shown to be consistent with the Arbabi-Sahimi suggestion that the ratio of the bulk to shear moduli approaches the value 8/z near threshold, where z is the coordination number. The frequency dependence of the scattering mean free path, l _s , was measured over an extended range of wave vectors k, corresponding to 1.6 < kl _s > 60, and spanning the transition from weak to very strong scattering. The mean free path was found to scale with a characteristic length, l _c, proportional to the percolation correlation length below which the structure exhibits fractal correlations. Comparison of the scaling behaviour for longitudinal and shear waves suggests that there may be a unique frequency for both polarizations, rather than a length scale, that characterizes the breakdown of the coherent propagation of acoustic waves due to very strong scattering.