Optimal Design Rules Research Articles

Heat pump and thermal energy storage: Influences of photovoltaic, the control strategy, and price assumptions on the optimal design

Combining heat pump, thermal energy storage, and photovoltaic is a common option to increase renewable energy usage in building energy systems. While research finds that optimal system design depends on the control, design guidelines neglect an influence of (1) photovoltaic, (2) the supervisory control, and (3) prices assumptions on the design of heat pump and thermal energy storage. We analyze how these influences may impact the optimal design. To analyze possible impacts, a pre-screening approach is used to identify relevant model input combinations with a potentially high influence on the optimal design. Applying a simulation-based design optimization with a detailed building energy system model, we optimize three cases: no photovoltaic, no supervisory control, and a state-of-the-art supervisory control. Results indicate that cost optimal design does not change with photovoltaic or the supervisory control, but heat pump size increases with higher electricity prices. For the storage, maximizing the size achieves high self-sufficiency degrees, but cost optimal design changes only for selected price assumptions. Overall, we find that neglecting photovoltaic and surplus control in the system design is a valid assumption. However, price assumptions should be included to allow simple but optimal design rules in current guidelines.

Mask-less Laser Direct Imaging & Adaptive Patterning for Fan-Out Heterogeneous Integration

Mask-less Laser Direct Imaging & Adaptive Patterning for Fan-Out Heterogeneous Integration

Complex-valued trainable activation function hardware using a TCO/silicon modulator

Artificial neural network-based electro-optic chipsets constitute a very promising platform because of its remarkable energy efficiency, dense wavelength parallelization possibilities and ultrafast modulation speeds, which can accelerate computation by many orders of magnitude. Furthermore, since the optical field carries information in both amplitude and phase, photonic hardware can be leveraged to naturally implement complex-valued neural networks (CVNNs). Operating with complex numbers may double the internal degrees of freedom as compared with real-valued neural networks, resulting in twice the size of the hardware network and, thus, increased performance in the convergence and stability properties. To this end, the present work revolves on the concept of CVNNs by offering a design, and simulation demonstration, for an electro-optical dual phase and amplitude modulator implemented by integrating a transparent conducting oxide (TCO) in a silicon waveguide structure. The design is powered by the enhancement of the optical-field confinement effect occurring at the epsilon-near-zero (ENZ) condition, which can be tuned electro-optically in TCOs. Operating near the ENZ resonance enables large changes on the real and imaginary parts of the TCO’s permittivity. In this way, phase and amplitude (dual) modulation can be achieved in single device. Optimal design rules are discussed in-depth by exploring device’s geometry and voltage-dependent effects of carrier accumulation inside the TCO film. The device is proposed as a complex-valued activation function for photonic neural systems and its performance tested by simulating the training of a photonic hardware neural network loaded with our custom activation function.

Study on CPI behaviors of X Dimension Fan-Out Integration (XDFOI) packages

XDFOITM (X Dimension Fan Out Integration) is a package family designed for fan out packages and heterogeneous integration, as XDFOI offers great flexibility to let single die or multi-functional chips, such as logic, memory, power management, RF and passive components, to be packaged by technology evolutions. Based on the approaches of “chip first” and “chip last” processes, XDFOI is designed with the high density I/O and multi-layer metals, polyimide and encapsulation materials like ABF, underfill or molding compound. Various materials applied in the full process flow brings lots of combination of CTE (coefficient of thermal expansion) and meanwhile the CTE mismatch may generate stress on the dielectric materials to influence the performance requirements. It is widely known that manufacturing procedures of heterogeneous integration make the boundaries of foundry backend process of line (BEOL) and bumping process fuzzy. In this paper, three package members in XDFOI family are introduced and the respective process flows are illustrated detailed in order to exhibit the differences between the solutions. Finite-element analysis is integrated along with package building process to predict the stress performances. The simulation results of XDFOI packages divided by packages provide a guideline for estimating maximum stress on the dielectric materials. In order to provide proper guideline to chip packages, data from theoretical calculation are collected, analyzed and merged into design rules for further process optimization and new product introduction. It is considered that the study can greatly improve the overall innovation level and process capabilities.

A Computationally Fast Method to Simulate Microwave-Heated Monoliths

Microwave-assisted process intensification is a promising technique hindered by the unavailability of design rules for optimization and scale-up. High-throughput computational models allowing the exploration of a vast design space are imperative for the rapid development and deployment of intensified microwave reactors. Recently, structured reactors, especially monoliths, are emerging as a canonical multiphase reactor setup in the microwave-heating community. The vast separation of scales in these reactors leads to a large number of mesh elements, making the simulations time-consuming and challenging to converge. To this end, we employ volume and asymptotic averaging to represent monoliths, a multiphase system consisting of a fluid and a solid phase, as a continuum or effective medium. We rigorously verify the adequacy of the averaging techniques to predict the spatiotemporal distribution of the electric field, electromagnetic power dissipation, and temperature against fully resolved monolith simulations. The developed continuum model can replicate the three-dimensional transient behavior obtained from the multiphase simulations with an order of magnitude lower computational expense. Moreover, the continuum model allows easier mesh generation and convergence of numerical solution than the multiphase model. The developed multiscale framework can be used to simulate microwave-heated monoliths and other multiphase reactors, such as packed beds and open-cell foams.

Design rules for optimization of photophysical and kinetic properties of azoarene photoswitches.

Azoarenes are an important class of molecular photoswitches that often undergo E → Z isomerization with ultraviolet light and have short Z-isomer lifetimes. Azobenzene has been a widely studied photoswitch for decades but can be poorly suited for photopharmacological applications due to its UV-light absorption and short-lived Z-isomer half-life (t1/2). Recently, diazo photoswitches with one or more thiophene rings in place of a phenyl ring have emerged as promising candidates, as they exhibit a stable photostationary state (98% E → Z conversion) and E-isomer absorption (λmax) in the visible light range (405 nm). In this work, we performed density functional theory calculations [PBE0-D3BJ/6-31+G(d,p)] on 26 hemi-azothiophenes, substituted with one phenyl ring and one thiophene ring on the diazo bond. We calculated the E-isomer absorption (λmax) and Z-isomer t1/2 for a set of 26 hemi-azothiophenes. We compared their properties to thiophene-based photoswitches that have been studied previously. We separated the 26 proposed photoswitches into four quadrants based on their λmax and t1/2 relative to past generations of hemi-azothiophene photoswitches. We note 8 hemi-azothiophenes with redshifted λmax and longer t1/2 than previous systems. Our top candidate has λmax and a t1/2 approaching 360 nm and 279 years, respectively. The results here present a pathway towards leveraging and optimizing two properties of photoswitches previously thought to be inversely related.

Integration of Back-Up Heaters in Retrofit Heat Pump Systems: Which to Choose, Where to Place, and How to Control?

Back-up heaters are essential for sustainable retrofit heat pump systems to achieve low capital costs and high system temperatures. Despite its importance, current literature focuses primarily on single aspects of the interaction between the back-up heater and the heat pump system. Furthermore, influences of varying scenarios are typically not considered. This paper simultaneously investigates the impact of 18 different scenarios on the optimal answer to the questions: Which back-up heater to choose, where to place it, and how to control it? A scenario consists of boundary conditions for weather, building envelope, radiator sizing, operational envelope, and the electricity-to-gas price/emission ratio, respectively. Using annual dynamic Modelica simulations, we evaluate and assess all interdependencies based on a full factorial design. We analyze final energy consumption, thermal comfort, and back-up heater as objectives. For gas-fired back-up heaters, the optimal placement and control align with current state-of-the-art recommendations. However, for electric back-up heaters, current guideline recommendations yield up to 30% higher operational costs and emissions compared to our findings. Consequently, future studies should develop optimal design rules for sustainable retrofit heat pump systems.

Chirp-Like Polyphase Sequence Based Discrete Circulant Transform Spread OFDM for Bandwidth-Limited IM/DD Systems

We propose and investigate chirp-like polyphase sequence (CLPS) based discrete circulant transform spread (DCrT-S) OFDM in bandwidth-limited intensity-modulation and direct-detection systems. This scheme can control the distribution of residual inter-symbol interference (ISI) and inter-carrier interference (ICI) across subcarriers by adjusting the CLPS's parameters. We also propose a sparse CLPS (SCLPS) scheme, by inserting zeros between the elements of the CLPS, to further balance the effects of the ISI/ICI and the noise and improve the performance by optimizing both the CLPS's parameters and the sparsity. We reveal the optimal design rule of CLPS/SCLPS analytically and investigate the performance of the proposed schemes using two-parameter CLPS in ∼110-Gbit/s simulations and experiments. It is shown that the optimal parameter vector of the CLPS is a Zadoff-Chu sequence that spreads the ISI/ICI more evenly over subcarriers. The performance is further improved by optimizing the sparsity. The optimal CLPS and sparsity are insensitive to the received optical power, the system bandwidth, the length of cyclic prefix, the chirp parameter and the signal data rate, and so can be pre-set without channel information. Both CLPS- and SCLPS-based DCrT-S-OFDM outperform Nyquist PAM, conventional OFDM, discrete-Fourier-transform spread (DFT-S) OFDM, and orthogonal-circulant-transform precoded (OCT-P) OFDM. By using the proposed scheme, the data rate is enhanced by 6.7% and 3.2% compared to DFT-S-OFDM and OCT-P-OFDM at a bit error rate (BER) of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> , while the complexity is reduced to 57.9% of OCT-P-OFDM.

Microfluidic electroless deposition for uniform stacking chip interconnection: Simulation framework and experimental validation

Microfluidic electroless deposition interconnection is a novel approach proposed and demonstrated for stacking chip application, but the deposition uniformity is observed as the key issue for further implementation. This work investigates the deposition uniformity in microchannel for stacking chip interconnection from the perspective of electrochemistry and fluid dynamics, demonstrating that the mass transfer behavior is the underlying mechanism for the uniformity. The effects of flow velocity, flow pattern, geometry parameters and hydrogen generation on mass transfer and deposition uniformity are studied and discussed by a validated simulation framework. The numerical results indicate that high velocity oscilloscope flow with small pad pitch is the optimal design rule for high uniformity. The non-uniformity of plating rate is improved to 0.004 μm/h for oscillatory flow, and gas volume friction is reduced to 0.018 with flow velocity of 200 μm/s. This work provides theoretical and systematic investigation and insight into the evolution mechanism for the application.

Characterization and optimization of gate driver turn-off voltage for eGaN HEMTs in a phase-leg configuration

Affected by high switching speed and parasitic parameters, crosstalk problem of eGaN HEMT in a phase-leg configuration cannot be ignored. By decreasing gate driver turn-off voltage, the false turn-on phenomenon of device caused by crosstalk can be avoided, but it is hard to realize the minimization of total power loss. Thus, we analyze the influence of gate driver turn-off voltage on eGaN HEMT reverse conduction loss, switching loss and crosstalk voltage, and propose an optimized design rules for determining turn-off voltage value in a phase-leg configuration. By reasonably choosing gate driver turn-off voltage, a balance between optimal loss and reliable operation is achieved, thereby effectively alleviating the conflict between efficiency and reliability in the power electronic system.

Optimal Transmit Coil Design for Wirelessly Powered Biomedical Implants Considering Magnetic Field Safety Constraints

This article presents an investigation on the optimal design of a transmit coil for a wireless power transfer system (WPTS) for biomedical implants with the goal of maximizing the magnetic flux density (B-field) at the location of the implant while not violating magnetic field exposure limits. Maximizing the B-field correlates to higher transferable electric power for certain WPTSs, such as those that use magnetoelectric receivers. While previous works have optimized the thermal efficiency, or system efficiency, to our knowledge no one yet has developed the procedure to optimize the transmitter to maximize the B-field subject to an imposed safety limit constraint for magnetic field exposure. In addition to this safety constraint, the optimal design of the transmitter is considered when the system geometry or the input current is constrained. Equations for determining the design parameters of an optimal solenoid transmitter are derived subject to constraints on either transmitter size or electric current. If a certain magnetic field strength is required, solutions to the size and current of the transmitter are presented, which allow the desired fields without violating the safety constraint. The mathematical model is experimentally validated, and a case study is described that illustrates the optimal design rules.

Numerical investigation into cleanability of support structures produced by powder bed fusion technology

PurposeSupport structures used in laser powder bed fusion are often difficult to clean from unsintered powder at the end of the process. This issue can be significantly reduced through a proper design of these auxiliary structures. This paper aims to investigate preliminary the airflow within differently oriented support structures and to provide design guidelines to enhance their cleanability, especially the depowdering of them.Design/methodology/approachThis study investigates the cleanability of support structures in powder bed fusion technology. Digital models of cleaning operations were designed through computer-aided engineering systems. Simulations of the airflow running into the powder entrapped within the thin walls of auxiliary supports were implemented by computational fluid dynamics. This approach was applied to a set of randomly generated geometrical configurations to determine the air turbulence intensity depending on their design.FindingsThe results, which are based on the assumption that a relationship exists between turbulence and powder removal effectiveness, demonstrated that the maximum cleanability is obtainable through specific relative rotations between consecutive support structures. Furthermore, it was possible to highlight the considerable influence of the auxiliary structures next to the fluid inlet. These relevant findings establish optimal design rules for the cleanability of parts manufactured by powder bed fusion processes.Originality/valueThis study presents a preliminary investigation into the cleanability of support structures in laser powder bed fusion, which has not been addressed by previous literature. The results allow for a better understanding of the fluid dynamics during cleaning operations. New guidelines to enhance the cleanability of support structures are provided based on the results of simulations.

Equivalent circuit model for the damping of micro-oscillators from molecular to viscous flow regime

This paper presents an equivalent circuit (EQC) model for describing the damping mechanism of micro-oscillators from the molecular flow regime up to the viscous flow regime. The EQC model consists of two parallel lines, representing the molecular and the viscous damping mechanism, respectively. The molecular line consists of an R–L circuit, which describes the intrinsic losses and the transfer of kinetic energy from the micro-oscillator to the surrounding gas molecules. The viscous line is formed by a resistor and a newly introduced inductive constant phase element. These elements represent the thermoviscous losses and the collision processes in the viscous flow regime. This EQC model was applied to the first fundamental bending mode of an oscillator vibrating in seven different types of gases (He, Ne, Ar, N2, CO2, N2O, SF6) as well as to the first five bending modes for another type of oscillator vibrating in nitrogen gas, only. In all cases, variations of an adjustable gap width to a fixed plate in the range of 150–3500 µm were also taken into account. The results from the presented EQC model are found to be in excellent agreement with the experimental data. Additionally, the electronic components of the EQC can be correlated to real physical properties of the setup, i.e. to the viscosity and density of the gas, as well as to the adjusted gap width and to the resonance frequency of the micro-oscillator. This allows the prediction of the quality factor curve of an oscillator over a large pressure range in a simple way for various configurations, concerning gas type, gap width, and bending mode/resonance frequency. Based on these results, an optimization model and design rules for enhancing the quality factor were derived.

Optical phase effects in reconfigurable microwave photonic filters with multiple wavelength input

Microwave photonic filters with a multiple wavelength input are analyzed. A comprehensive model assessing the impact of the phase characteristic of the optical stage is presented from which optimized design rules have been derived. Examples with one, 2 and 3 lasers are provided along with experimental results supporting our findings.

2D Phase Purity Determines Charge-Transfer Yield at 3D/2D Lead Halide Perovskite Heterojunctions

Targeted functionalization of 3D perovskite with a 2D passivation layer via R-NH3I treatment has emerged as an effective strategy for enhancing both the efficiency and chemical stability of ABX3 perovskite solar cells, but the underlying mechanisms behind these improvements remain unclear. Here, we assign a passivation mechanism where R-NH3I reacts with excess PbI2 in the MAPbI3 film and unsaturated PbI6 octahedra to form (R-NH3)2(MA)n-1PbnI3n+1. Crucially, we show that precise control of the 2D (R-NH3)2(MA)n-1PbnI3n+1 layer underpins performance improvements: n = 1 yields over a 2-fold improvement in hole injection to the HTL; n > 1 deteriorates hole injection. Ultrafast transient absorption spectroscopy suggests this n-dependence is rooted in the fact that fast (<6 ns) hole injection does not occur between the 3D and 2D layers. These results help explain contemporary empirical findings in the field and set out an important design rule for the further optimization of multidimensional perovskite optoelectronics.

Performance Optimization of FD-SOI Hall Sensors Via 3D TCAD Simulations.

This work investigates the behavior of fully depleted silicon-on-insulator (FD-SOI) Hall sensors with an emphasis on their physical parameters, namely the aspect ratio, doping concentration, and thicknesses. Via 3D-technology computer aided design (TCAD) simulations with a galvanomagnetic transport model, the performances of the Hall voltage, sensitivity, efficiency, offset voltage, and temperature characteristics are evaluated. The optimal structure of the sensor in the simulation has a sensitivity of 86.5 mV/T and an efficiency of 218.9 V/WT at the bias voltage of 5 V. In addition, the effects of bias, such as the gate voltage and substrate voltage, on performance are also simulated and analyzed. Optimal structure and bias design rules are proposed, as are some adjustable trade-offs that can be chosen by designers to meet their own Hall sensor requirements.

TCAD silicon device simulation for high level of radiation damage

Silicon detectors are expected to experience an unprecedented radiation flux in the future upgrades of the detectors at the Large Hadron Collider (LHC). The challenging radiation environment of these experiments will severely affect the performance of such detectors, degrading their detection capabilities and imposing severe operational conditions. The modeling of the detectors through Monte Carlo simulation represents a necessary step for the detailed understanding of the silicon detector performance before and after radiation damage; also for setting up optimized design rules aiming to mitigate the detrimental effect of the radiation damage. In the present work, a comparison of simulation results, obtained from- Technology Computer-Aided Design (TCAD) simulation software: Silvaco and Synopsys- used to predict silicon detectors performance, is presented. The effects of radiation damage are incorporated in the TCADs, using an effective multiple traps model. A systematic study of the sensitivity of the silicon detector's macroscopic parameters to the modeling of traps is performed. The simulation results for static electrical parameters, such as the leakage current and the full depletion voltage, obtained by the TCADs are presented and compared.

New Curved Reflectors for Significantly Enhanced Solar Power Generation in Four Seasons

A new curved-type reflector for solar power generation is proposed. By adopting the curved-type reflector between consecutive solar panel arrays, all incoming sunlight can be utilized and thus, the generated power is significantly increased. Furthermore, the proposed curved-type reflector can be generally used in four seasons regardless of the altitude or angle of the installation environment. The optimum design rule for the curved-reflector, comparing to a plane-type reflector, is completely developed in this paper. A new solar cell configuration best fit for the proposed curved-reflector is also provided. Experimental results showed that the curved-type reflector improves the spatial average solar power by 61% compared to no reflector case, which is even 11% higher than the plane-type reflector. Reflectors, especially curved-type reflectors, are found to be one of promising solutions for highly efficient solar power generation.

Parametric optimum design of a near-field electroluminescent refrigerator

A novel model of the irreversible near-field electroluminescent refrigerator (INFER) composed of an emitter and a receiver is proposed, where the heat transfers between the cold and hot sides and the reservoirs are taken into account. Based on the fluctuation electrodynamics, two critical formulas for the cooling power density (CPD) and cooling coefficient of performance (COP) of the INFER are derived. The optimum thermodynamic characteristics of the INFER are studied. Meanwhile, the effects of the vacuum gap on the performance of the INFER are discussed. By making a trade-off between the CPD and the COP, the parametric optimum design rules are presented. The parametric characteristics for homojunction and heterojunction structures are calculated and compared. An optimum design structure is determined. The results obtained here may provide some guidance for optimally designing and actually developing solid-state refrigerators.

Towards actuation improvement of low-profile piezo fibre composites by notched electrodes

The present contribution reports on a novel approach for enhanced piezoelectric patch transducers based on round piezoceramic fibres. Starting from a critical review of the well-known Active Fibre Composite (AFC) concerning electrical coupling between electrodes and ceramic fibres, a new electrode design is proposed. By introducing notches into the fibres perpendicular to their axis and filling these notches witch a conductor, a much better coupling is created. This leads to a significantly better alignment of the intrinsic dipoles over a wide volume of the fibres during poling and thus to much higher piezoelectric performance of the transducers. With the aid of a finite element analyses, design rules for optimization of notched electrodes as well as prediction of transducer behaviour have been derived. For verification of the approach, transducers with varying notch depths have been built and glued onto polystyrene beams attaining active cantilevers. The setup was used to measure free displacement and blocking force generated by the transducers in comparison to other existing patch transducers. An improvement of the piezoelectric actuation up to a factor of four is observed for free deflection and blocking force, significantly exceeding results from state-of-the-art patch transducers such as Macro Fiber Composites (MFC).