Extra Loss Research Articles

Influence of Dynamic Resistance on Current Distribution of HTS DC Cable Conductor for Feeder Lines and Large Scale Magnet

HTS DC cable conductors are promising because of high current density and intrinsic zero resistance. Therefore, HTS cable conductor with large current carrying capacity are expected to have widespread application in feeder lines and large scale magnets. At present, the conventional design of HTS cable conductor, general several of 10 kA, are designed with goal of uniform current distribution by adjusting winding pitch same as AC HTS cable since the ripple current is unavoidable in DC transmission line and AC current in process of exciting and demagnetizing is also alternative. Thus, AC magnetic field component generated on tapes of HTS cable conductor is non-negligible. If the AC magnetic field component is higher than the penetration field of the HTS tapes, there is inevitable dynamic resistance among them. Dynamic resistance is seldom considered in previously conventional design of DC cable conductors. The dynamic resistance significantly affects the current distribution among HTS tapes except for generating extra loss and incurring instability. Based on the conventional design method of uniform current, this paper presents the DC current distribution among layers by considering dynamic resistance, which is particularly much more significant for large current capacity HTS DC cable conductors with ripple currents.

InGaN Based C-Plane Blue Laser Diodes on Strain Relaxed Template with Reduced Absorption Loss

InGaN based c-plane blue LDs on strain relaxed template (SRT) with a reduced absorption loss was demonstrated. The loss is reduced from 27 cm−1 to 20 cm−1. Due to the lower loss, threshold current density is improved from 51.1 kA/cm2 to 43.7 kA/cm2, and slope efficiency is also increased by a factor of 1.22. The absorption loss from decomposition layer (DL) in SRT is confirmed to be a major extra loss source by both experimental and simulation results. With a higher indium content in buffer and waveguide layers, optical leakage into DL can be suppressed.

Improved adaptive EWMA control chart for process location with applications in groundwater physicochemical parameters and glass manufacturing industry.

The adaptive exponentially weighted moving average (AEWMA) control charts are the advanced form of classical memory control charts used for efficiently monitoring small-to-large shifts in the process parameters (location and/or dispersion). These AEWMA control charts estimate the unknown shifts using exponentially weighted moving average (EWMA) or cumulative sum (CUSUM) control charts statistics. The hybrid EWMA (HEWMA) control chart is preferred over classical memory control charts to detect early shifts in process parameters. So, this study presents a new auxiliary information-based (AIB) AEWMA (IAEWMAAIB) control chart for process location that estimates the unknown location shift using HEWMA statistic. The objective is to develop an unbiased location shift estimator using HEWMA statistic and then adaptively update the smoothing constant. The shift estimation using HEWMA statistic instead of EWMA or CUSUM statistics boosts the performance of the proposed IAEWMAAIB control chart. The Monte Carlo simulation technique is used to get the numerical results. Famous performance evaluation measures like average run length, extra quadratic loss, relative average run length, and performance comparison index are used to evaluate the performance of the proposed chart with existing counterparts. The comparison reveals the superiority of the proposed control chart. Finally, two real-life applications from the glass manufacturing industry and physicochemical parameters of groundwater are considered to show the proposed control chart’s implementation procedure and dominance.

How rainfalls influence urban traffic congestion and its associated economic losses at present and in future: taking cities in the Beijing-Tianjin-Hebei region, China for example?

Traffic congestion is one of serious problems in cities; rainfalls would exacerbate traffic congestion, and thus result in huge economic losses. However, limited studies focused on how rainfalls influenced traffic congestion and its associated economic losses. Based on detailed hourly data, we estimated how traffic congestion index (TCI) changed with different rainfall intensities in the Beijing-Tianjin-Hebei (BTH) region, and we also explored their economic losses. The results illustrated that all cities presented the similar trend of daily traffic congestion, and morning peak occurred 2 h later on holidays than workdays. Rainfall had significant impacts on traffic congestion for most time windows, except midnight. Traffic congestion increased with rainfall intensities, but smaller cities were more vulnerable to rainfall intensity than megacities. Rainfalls led to 0.95 billion yuan of extra economic losses in 2019, 38% of which occurred under heavy rainfalls. Traffic congestion in 2019 caused a total economic cost of 30.08 billion yuan in the BTH region (0.4% of its GDP), including the recurrent cost and economic losses due to rainfalls; besides, the social cost and direct cost contributed the same share of 49.5%, with 1% from the environmental costs. Considering future urban development and climate change, it is beneficial to establish the climate-resilient transportation system for avoiding future serious traffic congestion as well as huge economic losses in future.

Analysis of gap heat loss in external thermal insulation system of passive low-energy-consumption building based on CFD

The extra heat loss of a horizontal gap and a vertical gap formed by thermal insulation plate splicing is numerically studied by computational fluid dynamics. Three combinations of heat transfer modes are designed for three heat transfer modes, and the temperature, velocity distributions, and extra heat loss of the air layer in the gap under different combinations of heat transfer modes are obtained when the temperature difference is 22 K and the thickness of thermal insulation plate 300 mm, to determine the proportion of the heat loss of each heat transfer mode in the total heat loss. The results show that the main mode of heat loss in the horizontal gap is heat radiation, while the main mode of heat loss in the vertical gap is heat convection. The horizontal gap has little effect on heat loss, and the vertical gap has a great effect on heat loss.

High-Efficiency Broadband Grating Couplers for Silicon Hybrid Plasmonic Waveguides

We report the designs of on-chip grating couplers for the silicon hybrid plasmonic waveguides, which is the first proposal, to the best of our knowledge, for the direct coupling between a standard single-mode fiber and a hybrid plasmonic waveguide. By leveraging the apodized gratings and a two-stage-taper mode converter, we obtain a theoretical coupling efficiency of 79% (−1.03 dB) at the 1550 nm wavelength and a 3-dB bandwidth of 73 nm between the fiber and a 100 nm-wide silicon hybrid plasmonic waveguide with a bottom metal layer. We further propose grating couplers for three other sorts of silicon hybrid plasmonic waveguides with a metal cap and theoretically achieve good performances with coupling efficiencies larger than 47% and bandwidths larger than 51 nm. The proposed direct coupling scheme can avoid extra insertion losses and additional alignment processes that conventional indirect coupling schemes produce. It is believed to be a new step forward to the CMOS-compatible and large-scale integration based on the plasmonic waveguides.

Analysis of HCPV-LIB integrated hybrid system for renewable energy generation in Kuwait hot climate

In this work, a high concentrated photovoltaic system (HCPV) integrated with battery storage system is proposed to produce energy for different applications in hot harsh weather conditions of Kuwait. Integrated HCPV-battery storage units commonly deliver systems with higher energy density compared to systems with individual components due to less wiring as well as sharing usual electrodes and encapsulation. The principal motivation for employing HCPV for generating high energy is the significant improve in power output. In that case, large cell areas are replaced by more inexpensive optical concentrator resulting in a substantial reduction in system cost. Thermal and electrical models utilizing Kuwait weather conditions are developed to evaluate the performance of the different system components; HCPV module, battery, and converter. To examine the reliability and the advantages of the suggested system, its performance is compared to the corresponding system with individual components. The results of the developed models agree well with available experimental data. The errors in total root mean square of present outcomes are less than 2 %. Simulation results indicate that the temperature of the battery and converters significantly decreases by inserting an air gap of 6.5 cm thickness between HCPV module and the battery back. The maximum battery temperature does not exceed 41 °C under severe weather conditions which is lower than the maximum operation temperature recommended by battery manufacturer. The optimum capacity of HCPV generation and battery capacity are determined utilizing load of loss probability as a measure for comparison. The increase in the temperature of integrated HCPV-battery system results in extra power losses of about 2.7 % compared to normal solar HCPV system. Because of ambient temperature, the battery capacity decreases by 2.6 % after one year of operation. However, the high energy density of the integrated system because of common components compared to the normal HCPV system exceed the decrease in performance due to elevated module temperature.

Experimental Identification and Physical Interpretations of 2-D Tensor Magnetic Properties of a Grain-Oriented Electrical Steel Magnetized Between the Rolling and the Transverse Directions

This work investigates a 2-D vector field behavioral model to describe the anisotropic magnetic permeability and losses in Grain-Oriented Electrical Steels (GOES) within quasi-static and magneto-harmonic working conditions. The model includes the an-hysteretic magnetic field driven by the total anisotropy, the coercive force responsible for the quasi-static hysteresis losses, and the dynamic damping eddy field responsible for the extra losses. Each field contribution requires the definition of a tensor property whose diagonal and non-diagonal coupling components are experimentally identified as a function of the flux density magnitude <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B$ </tex-math></inline-formula> and its angle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta $ </tex-math></inline-formula> with the Rolling Direction (RD). The static behavior is identified at low frequency and the dynamic one takes the frequency-dependent field diffusion into account. Diagonalization tools reveal main characteristic magnetic axis for the separate properties with deflections at the macroscale.

Evolution of Main-sequence-like Surviving Companions in Type Ia Supernova Remnants

Recent theoretical and numerical studies of Type Ia supernovae (SNe Ia) explosions within the single-degenerate scenario suggest that the nondegenerate companions could survive during the supernova impact and could be detectable in nearby supernova remnants. However, observational efforts show less promising evidence of the existence of surviving companions from the standard single-degenerate channels. The spin-up/spin-down models are possible mechanisms to explain the nondetection of surviving companions. In these models, the spin-up phase could increase the critical mass for explosion, leading to a super-Chandrasekhar-mass explosion, and the spin-down phase could lead to extra mass loss and angular momentum redistribution. Since the spin-down timescale for the delayed explosion of a rotating white dwarf is unclear, in this paper we explore a vast parameter space of main-sequence-like surviving companions via two-dimensional hydrodynamic simulations of supernova impact and the subsequent stellar evolution of surviving companions. Tight universal relations to describe the mass-stripping effect, supernova kick, and depth of supernova heating are provided. Our results suggest that the not-yet-detected surviving companions from observations of nearby SN Ia remnants might favor low-mass companions, short binary separation, or stronger supernova explosion energies than the standard single-degenerate channels.

Proposal for transduction between microwave and optical photons using Er167 -doped yttrium orthosilicate

Efficient transduction devices that reversibly convert optical and microwave quantum signals into each other are essential for integrating different technologies. Rare-earth ions in solids, and in particular Erbium ions, with both optical and microwave addressable transitions are promising candidates for designing transducers. We propose a microwave-to-optical quantum transducer scheme based on the dark state protocol in $\mathrm{^{167}Er}$ doped into yttrium orthosilicate (YSO) at zero external magnetic fields. Zero-field operation is beneficial for superconducting resonators that can incur extra losses in magnetic fields. By calculating the fidelity and efficiency of the transducer, considering the most important imperfections, we show that an efficient conversion is possible with a high fidelity. We also investigate the microwave transitions of $\mathrm{^{167}Er}$:YSO that can be used for the transducer protocol.

Numerical studies on the combustion of ultra-low calorific gas in a divergent porous burner with heat recovery

This study presents the idea of heat recovery through recirculating walls to enhance the combustion stability for ultra-low calorific gas in a porous burner. Numerical studies on the combustion of ultra-low calorific gas of CO/H2 with CO2 and N2 in a developed divergent porous burner with annular channel is conducted using two-dimensional axis symmetrical model with detailed kinetics. The heat recovery efficiency is defined as the ratio of heat recovery by the fresh mixture in the annular channel to burner power. It is shown that the heat recovery has significant effect on the minimal inlet gas temperature (MIGT) for stable combustion. It is confirmed that the heat recovery enhances the combustion and the stability limits are enlarged by preheating the fresh mixture, but it also leads to an extra pressure loss across the burner compared to that without heat recovery. Results show that heat recovery efficiency reaches up to 0.18 for all the investigated parameters and it reduces linearly from 0.32 to 0.18 as the mass flow ratio increases from 0.8 to 1.5. The MIGT for the burner with heat recirculating channel is always smaller than that without heat recovery. As a result, the combustion is greatly improved by the heat recovery in the divergent burner. Meanwhile, it is shown that pressure loss is increased significantly when the heat recirculating annular channel is added.

Path Loss Model for 3.5 GHz and 5.6 GHz Bands in Cascaded Tunnel Environments.

An important and typical scenario of radio propagation in a railway or subway tunnel environment is the cascaded straight and curved tunnel. In this paper, we propose a joint path loss model for cascaded tunnels at 3.5 GHz and 5.6 GHz frequency bands. By combining the waveguide mode theory and the method of shooting and bouncing ray (SBR), it is found that the curvature of tunnels introduces an extra loss in the far-field region, which can be modeled as a linear function of the propagation distance of the signal in the curved tunnel. The channel of the cascaded straight and curved tunnel is thus characterized using the extra loss coefficient (ELC). Based on the ray-tracing (RT) method, an empirical formula between ELC and the radius of the curvature is provided for 3.5 GHz and 5.6 GHz, respectively. Finally, the accuracy of the proposed model is verified by measurement and simulation results. It is shown that the proposed model can predict path loss in cascaded tunnels with desirable accuracy and low complexity.

Tunable In-series Laser Array With Duplex Distributed Feedback Sections

The tunable laser based on distributed feedback (DFB) laser array has a good single-longitudinal-mode property, high wavelength stability, narrow spectrum linewidth, and feasibility for monolithic integration. The tunable in-series DFB laser array (TIDLA) was proposed to avoid the large extra power loss by the optical combiner. But in the TIDLA, a large laser count will cause a large chip length, which brings about low utilization ratio of material, poor mechanical strength, and large power consumption. In this paper, we demonstrated a 4-channel TIDLA with duplex DFB sections. The total chip length was greatly shortened owing the duplexing of DFB sections. A long linearly chirped Bragg grating is implemented in the laser cavity to reduce the grating interference among different lasers. Multiple π phase shifts and two reflector sections are introduced to improve the mode stability. The designed channel spacing is 100 GHz, and the reconstruction-equivalent-chirp technique is used to provide high precision control of the grating phase. Noted that a variation of 0.1 nm in grating period will cause that of 0.65 nm in wavelength. Output power of above 4 mW, SMSR of above 42 dB, and small wavelength deviation of within 0.15 nm was obtained. Besides, fast channel switches of less than 1 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> s are obtained by laser on/off switching. The proposed TIDLA might be applied in the NG-PON2 network where the dense wavelength division multiplexing technique and fast channel switching are required.

An Adaptive EWMA Control Chart Based on Principal Component Method to Monitor Process Mean Vector

The special causes of variations, which is also known as a shift, can occur in a single or more than one related process characteristics. Statistical process control tools such as control charts are useful to monitor shifts in the process parameters (location and/or dispersion). In real-life situation, the shift is emerging in different sizes, and it is hard to identify it with classical control charts. Moreover, more than one process of characteristics required special attention because they must monitor jointly due to the association among them. This study offers two adaptive control charts to monitor the different sizes of a shift in the process mean vector. The novelty behind this study is to use dimensionally reduction techniques such as principal component analysis (PCA) and an adaptive method such as Huber and Bi-square functions. In brief, the multivariate cumulative sum control chart based on PCA is designed, and its plotting statistic is utilized as an input in the classical exponentially weighted moving average (EWMA) control chart. The run length (RL) properties of the proposed and other control charts are obtained by designing algorithms in MATLAB through a Monte Carlo simulation. For a single shift, the performance of the control charts is assessed through an average of RL, standard deviation of RL, and standard error of RL. Likewise, overall performance measures such as extra quadratic loss, relative ARL, and the performance comparison index are also used. The comparison reveals the superiority over other control charts. Furthermore, to emphasize the application process and benefits of the proposed control charts, a real-life example of the wind turbine process is included.

A new generative adversarial network for medical images super resolution

For medical image analysis, there is always an immense need for rich details in an image. Typically, the diagnosis will be served best if the fine details in the image are retained and the image is available in high resolution. In medical imaging, acquiring high-resolution images is challenging and costly as it requires sophisticated and expensive instruments, trained human resources, and often causes operation delays. Deep learning based super resolution techniques can help us to extract rich details from a low-resolution image acquired using the existing devices. In this paper, we propose a new Generative Adversarial Network (GAN) based architecture for medical images, which maps low-resolution medical images to high-resolution images. The proposed architecture is divided into three steps. In the first step, we use a multi-path architecture to extract shallow features on multiple scales instead of single scale. In the second step, we use a ResNet34 architecture to extract deep features and upscale the features map by a factor of two. In the third step, we extract features of the upscaled version of the image using a residual connection-based mini-CNN and again upscale the feature map by a factor of two. The progressive upscaling overcomes the limitation for previous methods in generating true colors. Finally, we use a reconstruction convolutional layer to map back the upscaled features to a high-resolution image. Our addition of an extra loss term helps in overcoming large errors, thus, generating more realistic and smooth images. We evaluate the proposed architecture on four different medical image modalities: (1) the DRIVE and STARE datasets of retinal fundoscopy images, (2) the BraTS dataset of brain MRI, (3) the ISIC skin cancer dataset of dermoscopy images, and (4) the CAMUS dataset of cardiac ultrasound images. The proposed architecture achieves superior accuracy compared to other state-of-the-art super-resolution architectures.

Stability improvement without efficiency penalty of a transonic centrifugal compressor by casing treatment and impeller/diffuser coupling optimization

Self-recirculation casing treatment (SRCT) is usually used to improve the flow stability of centrifugal compressors, while extra aerodynamic losses are often introduced. It is challenging to remove the efficiency penalty for the design of SRCT. In this study, a coupling optimization is implemented to redesign a transonic centrifugal compressor with an SRCT. Firstly, the physical design space is expanded to include the design parameters of both the SRCT and the impeller/diffuser. Secondly, data-mining techniques are used to explore and refine the expanded design space. Consequently, seven critical design parameters are quantitatively identified, and they generally present non-linear and trade-off correlations with the compressor performances. Then, the global optimization is carried out for the refined design space. As a result, significant improvements of the aerodynamic performances of the compressor are obtained. The efficiency penalty introduced by the SRCT is eliminated, and the stable flow range is maintained simultaneously. This is infeasible for the single redesign of the SRCT or the impeller/diffuser. The flow mechanisms of the coupling optimization are as follows. The recirculation flow rate of the SRCT is increased, and more low-energy fluid near the shroud is removed. The incidence angle and the leading-edge blade loading at high spanwise region of the impeller are reduced. The interaction between the tip leakage vortex and the inducer shock wave is delayed and weakened. The inlet mixing loss and the inlet radial distortion of the impeller are decreased. The friction loss is reduced and the flow separation is suppressed in the vaned diffuser.

A Power Quality Improved EV Charger by Using Bridgeless CUK Converter

Abstract: This study designs and develops an improved bridgeless (BL) Cuk converter-based electric vehicle (EV) battery charger with a high-power factor and higher efficiency. It offers a low-cost, high-power-density-based charging solution for EVs. This charger has fewer components functioning during a single switching cycle, which decreases the extra conduction loss experienced by the typical charger's diode bridge rectifier. As a result, it boosts the charger's efficiency. The suggested topology also avoids the undesired capacitive coupling loop and unwanted conduction via the body diode of the inactive switch in the previously developed BL Cuk converter. This considerably enhances the charger's efficiency. A flyback converter synchronises the orders for constant current and constant voltage charging. The suggested charger draws a sinusoidal current from an alternating current main, and the overall harmonic distortion in the supply current is kept within the IEC 61000-3-2 requirements. The suggested charger's increased efficiency and power quality indices are studied to verify its good charging performance under all operational situations. Keywords: Bridgeless (BL) Cuk converter, discontinuous conduction mode (DCM), flyback converter, power factor correction (PFC), and power quality are all terms used to describe a battery charger (PQ).

Efficient Auxiliary Information–Based Control Charting Schemes for the Process Dispersion with Application of Glass Manufacturing Industry

The hybrid exponentially weighted moving average (HEWMA) control chart is an enhanced version of the EWMA control chart that monitors the process parameters effectively. Similarly, the auxiliary information-based (AIB) EWMA control charts are very efficient for monitoring process parameters. The purpose of this paper is to propose two new control charts for the improved monitoring of process dispersion referred to as HEWMA AIB 1 and HEWMA AIB 2 control charts. A simulation study is carried out to assess the performance of the proposed HEWMA AIB 1 and HEWMA AIB 2 control charts. Average run length, extra quadratic loss, relative average run length, and performance comparison index are used to compare the performance of the proposed control charts against the existing counterparts. The comparisons reveal the superiority of the proposed control charts against other competing control charts, particularly for small to moderate shifts in the process dispersion. Finally, a real-life data set from the glass industry is used to demonstrate the practical implementation of the proposed control charts.

Analysis of local burnout in a sub-scale test coil for the 32 T magnet after spontaneous quenches during fast ramping

Industrial production of REBa2Cu3O7-δ (REBCO) coated conductors has made it possible to construct the 32 T magnet, the first successful all-superconducting user magnet to exceed 30 T, which now serves users as SCM4 (superconducting magnet) at the NHMFL. Here, we present an analysis of the damage that occurred in late-stage proof testing of the 32 T prototype coil after many essential facets of the design had been proven through more than 100 intentionally triggered quenches at fields up to 24 T. This prototype coil was then subjected to accelerated charge–discharge cycles at a rate 44 times faster than its design ramp rate in an attempt to address its fatigue tolerance. The extra hysteresis loss of the fast ramps led to heating of the end pancakes, which was induced after 55 fatigue cycles, three spontaneous quenches at progressively lower currents. Recognizing that the coil was damaged, the pancakes were then unwound and their REBCO tapes run through our continuous in-field transport I c and remnant-field magnetization monitoring device, YateStar, which revealed three highly localized zones of low I c in the end pancake that induced quench. Careful examination of these zones, especially the most intensely damaged one, revealed that the worst hot spot reached at least 779 °C during the quenches. Magneto-optical imaging showed that this damaged zone was about 5 mm in diameter and indeed the perpendicular damage length induced in neighboring turns by this localized quench heating was almost as great. Although there is much present concern about fatigue crack propagation from edge defects, we actually attribute this damage not to fatigue but to fluctuations in vortex pinning density due to imperfect BaZrO3 (BZO) nanorod growth that locally reduced the critical current I c. These localized low-I c regions then had to shed their excess current into the copper stabilizer, producing intense heating. We provide transmission and scanning electron microscopy evidence for local fluctuations of the BZO pinning structure and relate it to recent work that shows significant variations of 4 K, high field I c values due to apparent production fluctuations of the growth conditions of the Zr-doped metal-organic chemical vapor deposition REBCO used for this test magnet.

Experimental and Numerical Flow Analysis of an Engine Realistic State-of-the-Art Turbine Rear Structure

Abstract This paper presents experimental and numerical CFD studies of the aerodynamics of a turbine rear structure (TRS). The TRS test geometry is an engine-realistic state-of-the-art design with a polygonal outer case, recessed engine mount bumps, and three different vane types: regular vanes, bump vanes in bump sectors, and thick vanes. Using three different sector types simultaneously was found to be crucial for the inlet boundary conditions. Experiments were performed in a modern rotating test facility with a low-pressure turbine (LPT) stage upstream of the TRS. A Reynolds number of 350,000 was used, representative of a TRS in a narrow-body geared turbofan engine. The TRS performance was analyzed both at on- and off-design conditions, and a thorough side-by-side comparison of CFD and experiments was performed. Static-pressure distributions, turning and outlet flow-angles, wakes and losses, and surface-flow visualizations and outlet total pressure contours are presented. The thick vane showed good aerodynamic performance, similar to the regular vane. For the bump vane, the mount bumps were found to generate additional local separations and secondary flows, resulting in extra losses. In the regions with strong secondary flows, CFD over-predicts the wakes, whereas the wakes around midspan, where secondary flows have a smaller influence, are predicted well.