Dual-source System Research Articles

Dual-Source Self-Start High-Efficiency Microscale Smart Energy Harvesting System for IoT

This paper presents a low-power batteryless energy harvesting system for Internet of Things (IoT) applications. A dual-mode dc–dc converter is used to harvest the energy of a microscale photovoltaic (PV) transducer and provides energy, in the boost mode, to a super capacitor for storage. In the buck mode, the dc–dc converter provides energy to the load on demand. A piezoelectric transducer is used as a secondary input source to guarantee system self startup. The proposed system includes a smart control to adaptively adjust the number of sensors at the load, leading to better usage of the available energy at any given time. The implementation also includes a programmable switch sizing to optimize the overall system's efficiency for different load conditions. A maximum power point tracking is used to extract the maximum power of the PV transducer under various illumination conditions. The system has been implemented in a CMOS 130-nm technology and tested in various modes of operation. Self startup has been verified, and a peak efficiency of 90.5% has been measured.

Artificial neural network model for cost optimization in a dual-source multi-destination outbound system

Cost optimization is one of the most important issues in distribution operations of any manufacturing system. Most real life problems are non-deterministic polynomial-time hard, and solving such pr...

On the Performance of Tailored Base-Surge Policies: Theory and Application at Walmart.Com

Problem Definition: Many import items sold at Walmart.com have two suppliers: one is faster and has a random production capacity limit while the other is slower and has infinite capacity. The lead time difference of the two suppliers could be as large as 12 weeks. Walmart.com faces an important and challenging supply chain problem and must make routine inventory replenishment decisions. Academic/Practical Relevance: Dual-sourcing inventory models have been extensively studied in academia and dual-sourcing strategies have been widely implemented in practice. Recently, the so-called Tailored Base-Surge (TBS) policy has begun to receive more attention and demonstrated good performance in existing dual-sourcing models. TBS is intuitive and easy to manage: a constant-order is placed from the slow (regular) supplier every period and a base-stock policy is adapted from the fast (express) supplier. Methodology: This paper develops a new dual-sourcing inventory model incorporating large lead time difference as well as random capacity of the express supplier, and investigates the performance of TBS both theoretically and empirically by using Walmart’s data. Results: We prove that a TBS policy is asymptotically optimal as the regular lead time grows, extending the previous asymptotic optimality of TBS policies in the dual-sourcing system without random capacities. We complement the theory and compare TBS with three well-known heuristics in a “simulated” real-world setting through model calibration by using historical sales data from Walmart.com. Our results demonstrate that TBS outperforms others as for minimizing the long-run average inventory cost. In particular, the inventory cost would be reduced by at least 33% if adapting a TBS policy. Our results also suggest that at an aggregate level, TBS could reduce Weeks of Supply by 2.7 weeks while increasing Met Demand by 3.3% compared with the single-sourcing policy using only the import supplier. Managerial Implications: Our results show that if the proposed dual-sourcing model and algorithm are adapted, Walmart’s inventory system would be significantly improved especially for import items.

Air–water dual-source heat pump system with new composite evaporator

Several renewable energy sources based on composite heat pump technology, which has been gaining increasing attention, are combined for application in building areas to obtain high operation efficiency and maximize energy saving. In this study, two kinds of air–water dual-source composite evaporators, namely, evA and evB (a new type), are proposed and air–water dual-source composite heat pump (AWSHP) systems with evA and evB are established. The AWSHP-evA and AWSHP-evB systems can be run in different modes, including air source heating mode (ASHM), water source heating mode (WSHM), and air–water source heating mode (AWSHM). The AWSHP-evB system has several advantages over the AWSHP-evA system, such as better coefficient of performance (COP), wider ambient temperature range for the efficient operation of AWSHM, and several different defrosting modes. A comparison of the experimental results obtained under different test conditions shows that COPWSHM of AWSHP-evB can be enhanced by 6.3% to 9.8%, whereas COPASHM of AWSHP-evA and AWSHP-evB are identical. Meanwhile, COPAWSHM of AWSHP-evB system can be enhanced by 8.8% to 13.3% in test conditions when hot water temperature is increased from 18 ± 1.0 °C to 51 ± 1.0 °C.

Leaflet thrombosis following transcatheter aortic valve implantation

BackgroundTranscatheter aortic valve implantation (TAVI) is increasingly being offered to high-risk patients with symptomatic aortic valve stenosis. Recent reports have suggested a high incidence of subclinical leaflet thrombosis following bioprosthestic aortic valve replacement. We report the frequency and clinical presentation of leaflet thrombosis identified by cardiac CT in patients referred for follow-up contrast enhanced CT angiography following TAVI. Methods91 consecutive patients referred for follow-up contrast-enhanced CT angiography following TAVI were screened for inclusion in this analysis. Out of these, 13 patients were excluded. All CT examinations were performed using a 2nd or a 3rd generation dual-source system (Somatom Definition Flash/Force, Forchheim, Germany). In all patients, retrospectively ECG-gated spiral acquisition with tube modulation was performed to allow for assessment of leaflet motion. All prostheses were analyzed for presence of leaflet thrombosis defined as hypo-attenuated leaflet thickening with or without leaflet restriction. Post-procedural antithrombotic regimen as well as symptom status was documented in all patients. Results78 consecutive patients (35 males, 81 ± 4 years) were analyzed. TAVI had been performed in all patients (76 transfemoral access, 2 transapical access) with either balloon-expandable prostheses (4 Sapien XT, 64 Sapien 3) or self-expandable prostheses (5 SJM Portico, 5 Symetis Acurate). Follow-up CT angiography was performed at a median of 4 months following index procedure (Interquartile range 1 month). Leaflet thrombosis was detected in 18 patients (23%, 14 Sapien 3, 1 Sapien XT, 2 SJM Portico, 1 Symetis Acurate). In patients with leaflet thickening on CT, only 11% were on either oral anticoagulation or new oral anticoagulants versus 50% for patients with no leaflet thickening (p 0.002). In patients with leaflet thrombosis, 3 leaflets were affected in 5 patients, 2 leaflets in 5 patients and in 8 patient only 1 leaflet was affected. Clinical symptoms (angina, dyspnea or both) were reported in 2/18 patients with leaflet thrombosis (11%) and in both patients a significant increase of the mean echocardiographic gradient over the prosthesis was documented. The peak and mean echocardiographic gradients obtained at the day of CT examination was significantly higher in symptomatic patients versus asymptomatic patients (peak 46 ± 7 vs. 23 ± 11 mmHg, mean 29 ± 7 vs. 12 ± 6 mmHg, p = 0.01 and 0.002, respectively).Follow-up CT was available for 4 patients with complete resolution of the hypo-attenuated leaflet thickening following treatment. ConclusionLeaflet thrombosis following TAVI is a relatively frequent finding in patients referred for contrast enhanced CT angiography following TAVI. In the majority of patients it follows a subclinical course and is substantially more frequent in individuals who are not on oral anticoagulation. However, in patients with relevant increase in prosthetic gradients, symptomatic presentations are possible.

Study of a Novel Dual-source Chemisorption Power Generation System Using Scroll Expander

A dual-source chemisorption power generation system using scroll expander is proposed and studied to recover dual heat sources under various working conditions. The chemisorption power generation system mainly composes of two adsorption beds and two expansion machines for the purpose of recovering low grade heat energy such as solar energy and industrial waste heat into electricity. The performance evaluation of the system with Six Metal Chlorides-Ammonia working pairs and scroll expander as the expansion device has been conducted to identify the optimal operational conditions of the system. Results indicate MnCl2-SrCl2 is the optimal working pair while the first heat source temperature is from 90 oC to 220 oC. NiCl2-SrCl2 is suitable to be used when the first heat source temperature is higher than 220 oC. Considering about the specific energy and operational condition of the scroll expander, the optimal working pair of the system is achieved by MnCl2-SrCl2 while the first heat source temperature from 180 to 200 oC and the second heat source temperature from 80 to 90 oC. The average specific energy of the system under the suggested conditions can be as high as 102 kJ/kg salts for Mode 1 and 85 kJ/kg salts for Mode 2 with the overall average thermal efficiency at 10%.

Load Prediction and Distributed Optimal Control of On-Board Battery Systems for Dual-Source Trolleybuses

Dual-source electric vehicles powered by both on-board battery and grid electricity offer unique advantages in fuel economy, cost reduction, driveability, and grid support, which are especially appealing for public transportation in populated cities. The structures of their power supply systems create naturally a networked system of vehicles sharing common feeders. Their power management and control strategies must individually enhance each vehicle’s local performance, and coordinate globally to limit the grid peak current, reduce current fluctuations, and improve efficiency. This paper introduces a novel methodology that employs load prediction, optimal control, and distributed predictive control for current management in such networked systems without vehicle-to-vehicle communications. Estimation and control strategies are introduced, and computationally efficient recursive algorithms are developed. The power system configuration of the Beijing dual-source trolleybus system is used for simulation case studies on the new management strategies. Estimation accuracy, prediction reliability, and performance improvement from the integrated predictive control strategies are demonstrated. Successful implementation of the methodology can potentially attenuate feeder current fluctuations, reduce feeder peak loads, and alleviate disturbances to main grids.

Dual Sourcing Inventory Systems: On Optimal Policies and the Value of Costless Returns

We study dual sourcing inventory systems with backordering and with stationary, stochastic demands. The two supply sources differ in their unit prices and lead times. We focus on the option of making costless returns to the cheaper, longer leadtime supplier. We show that the value of this option is zero. Our analysis leading to this result includes the derivation of several structural properties of the optimal policies for dual sourcing systems with and without the return option.

Coronary lesion complexity assessed by SYNTAX score in 256-slice dual-source MDCT angiography

The SYNTAX Score (SS) has an important role in grading the complexity of coronary artery disease (CAD) in patients undergoing revascularization. Noninvasive determination of SS prior to invasive coronary angiography (ICA) might optimize patient management. We aimed to evaluate the agreement between ICA and multidetector computed tomography (MDCT) while testing the diagnostic effectiveness of SS-MDCT. Our study included 108 consecutive patients who underwent both MDCT angiography with a 256-slice dual-source MDCT system and ICA within 14±3 days. SS was calculated for both ICA and MDCT coronary angiography. Spearman's rank correlation coefficient was used to evaluate the association of SS-MDCT with SS-ICA, and Bland-Altman analysis was performed. The degree of agreement between SS-ICA and SS-MDCT was moderate. The mean SS-MDCT was 14.5, whereas the mean SS-ICA was 15.9. After dividing SS into three groups (high [≥33], intermediate [23-32], and low [≤22] subgroups), agreement analysis was repeated. There was a significant correlation between SS-MDCT and SS-ICA in the low SS group (r=0.63, P = 0.043) but no significant correlation in the high SS group (r=0.036, P = 0.677). The inter-test agreement analysis showed at least moderate agreement, whereas thrombotic lesions and the type of bifurcation lesion showed fair agreement. The calculation of SS-MDCT by adapting SS-ICA parameters achieved nearly the same degree of precision as SS-ICA and was better than SS-ICA, especially in the low SS group.

Is ECG triggering for motion artefact reduction in dual-source CT angiography of the ascending aorta still required with high-pitch scanning? The role of ECG-gating in high-pitch dual-source CT of the ascending aorta.

To compare electrocardiographic (ECG)-triggered high-pitch (HP) dual-source CT angiography (CTA) with non-ECG-triggered HP CTA of the aorta, particularly the ascending aorta, with regard to image quality, motion artefacts, contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR) and radiation dose. 59 consecutive patients who had been referred for CTA for known or suspected aortic disease, previous aortic intervention or planned transapical or transfemoral aortic valve implantation were prospectively included. Patients underwent CTAs with HP, using a dual-source CTA system, with [control group (Group A); n = 30] or without (Group B; n = 29) ECG triggering after randomization. For evaluation, image quality and a motion artefact score (MAS) were assessed in a blinded fashion at different predefined anatomic regions. CNR and SNR were measured at the same levels. Radiation dose estimates and contrast enhancement were compared between the two groups. There were no significant differences for image quality and MAS. The intra-arterial contrast resolution was significantly higher at the level of the aortic arch and descending aorta in the non-triggered group (CNR values, p = 0.002-0.018). No significant differences in the radiation dose were found. Non-triggered HP dual-source CTA provided comparable results with regard to image quality, MAS, CNR, SNR and radiation doses compared with ECG-triggered HP CTA. Therefore, ECG triggering of the ascending aorta might be obviated when HP scanning is available. HP dual-source CTA might obviate ECG triggering in the ascending aorta. Non-triggered HP CTA of the ascending aorta provides an excellent image quality.

Simulation analysis on dynamic performance of a combined solar/air dual source heat pump water heater

This paper investigated a combined solar/air dual source heat pump water heater system for domestic water heating application. In the dual source system, an additional air source evaporator is introduced in parallel way based on a conventional direct expansion solar-assisted heat pump water heaters (DX-SHPWH) system, which can improve the performance of the DX-SHPWH system at a low solar radiation. In the present study, a dynamic mathematical model based on zoned lump parameter approach is developed to simulate the performance of the system (i.e. a modified DX-SHPWH (M-DX-SHPWH) system). Using the model, the performance of M-DX-SHPWH system is evaluated and then compared with that of the conventional DX-SHPWH system. The simulation results show the M-DX-SHPWH system has a better performance than that of the conventional DX-SHPWH system. At a low solar radiation of 100W/m2, the heating time of the M-DX-SHPWH decreases by 19.8% compared to the DX-SHPWH when water temperature reaches 55°C. Meanwhile, the COP on average increases by 14.1%. In addition, the refrigerant mass flow rate distribution in the air source evaporator and the solar collector of the system, the allocation between the air source evaporator and the solar collector areas and effects of solar radiation and ambient air temperature on the system performance are discussed.

Robust and Scalable Management of Power Networks in Dual-Source Trolleybus Systems: A Consensus Control Framework

Dual-source trolleybuses powered by onboard battery and grid electricity offer unique advantages in fuel economy, cost reduction, and passenger capacity, which are particularly appealing for public transportation in populated cities. Their mobility and power supply network configurations introduce challenging power management issues on their dedicated supply power grids. To ensure safe, reliable, and efficient operation of trolleybuses, their high-current and dynamic loads must be distributed to the feeders properly and promptly. Based on certain emerging networks of feeders and supply stations for city trolleybus systems, this paper introduces a new framework for current flow balancing based on recently developed weighted-and-constrained consensus control methods to manage the power supply network. Using only neighborhood information exchange among feeder lines in the network, the consensus control can achieve global current balancing with fast convergence to a balanced state, robustness to load perturbations, reconfiguration with feeder addition and deletion, and rebalancing under feeder capacity variation. The methodology is scalable in the sense that system expansion will not substantially increase the control system complexity. The power system configurations of the Beijing dual-source trolleybus system are used for simulation case studies on the new power management methods. Robustness and scalability are demonstrated, together with discussions on the feasibility, flexibility, and implementation issues of the methodology.

Optical Characteristic and Application of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> Thin Film in Schottky Diode

CH3NH3PbI3 thin film was deposited by a dual-source evaporation system under high vacuum (∼10−4 Pa). The crystallographic phase was analyzed by X-ray diffraction and confirmed as the perovskite structure. The optical properties of the thin film have been investigated in the spectral range 300-1800 nm. The analysis of the absorption coefficient () reveals direct allowed transition with corresponding energy 1.58 eV. The surface morphology of the film was characterized by atomic force microscopy (AFM). The observed features exhibited by CH3NH3PbI3 give a vital chance to explore its application for various optoelectronic devices. To see its other potential utility, Al/CH3NH3PbI3 /ITO Schottky diodes were fabricated. Based on the analyzing the I-V measurement for the Al/CH3NH3PbI3/ ITO device, the basic device parameters such as barrier height and ideality factor were determined. At the low-voltage region, the current conduction in the device is ohmic type. The charge transport phenomenon appears to be space charge limited current (SCLC) at higher-voltage regions.

Organometallic hybrid perovskites: structural, optical characteristic and application in Schottky diode

CH3NH3PbI3 thin film was deposited by a dual-source evaporation system under high vacuum (~10−4 Pa). The crystallographic phase of the thin film was determined by X-ray diffraction and its perovskite structure was confirmed. The crystal of annealed perovskite film was extremely smooth and significantly larger than that of as-deposited. The optical property of the thin film was investigated in the spectral range 300–1800 nm. By analyzing the absorption coefficient (α), the optical band gap (1.58 eV) and Urbach energy (0.082 eV) were revealed. The Al/CH3NH3PbI3/ITO Schottky diode was fabricated in order to explore the potential applications of CH3NH3PbI3. The basic device parameters, barrier height and ideality factor were determined by the current–voltage (I–V) measurement. It can be found that the charge transport was governed by space-charge-limited current mechanism by studying the forward bias characteristic.

Acquisition Pricing and Inventory Decisions on Dual-Source Spare-Part System with Final Production and Remanufacturing

The life spans of durable goods are longer than their warranty periods. To satisfy the service demand of spare parts and keep the market competition advantage, enterprises have to maintain the longer inventory planning of spare parts. However, how to obtain a valid number of spare parts is difficult for those enterprises. In this paper, we consider a spare-part inventory problem, where the inventory can be replenished by two ways including the final production order and the remanufacturing way. Especially for the remanufacturing way, we consider the acquisition management problem of used products concerning an acquisition pricing decision. In a multiperiod setting, we formulate the problem into a dynamic optimization problem, where the system decisions include the final production order and acquisition price of used products at each period. By stochastic dynamic programming, we obtain the optimal policy of the acquisition pricing at each period and give the optimal policy structure of the optimization problem at the first period. Then, a recursion algorithm is designed to calculate the optimal decisions and the critical points in the policy. Finally, the numerical analyses show the effects of demand information and customer’s sensitive degree on the related decisions and the optimal cost.

Dual energy CT with photon counting and dual source systems: comparative evaluation

Recently, new dual energy (DE) computed tomography (CT) systems—dual source CT (DSCT) and photon counting CT (PCCT) have been introduced. Although these systems have the same clinical targets, they have major differences as they use dual and single kVp acquisitions and different x-ray detection and energy resolution concepts. The purpose of this study was theoretical and experimental comparisons of DSCT and PCCT. The DSCT Siemens Somatom Flash was modeled for simulation study. The PCCT had the same configuration as DSCT except it used a photon counting detector. The soft tissue phantoms with 20, 30, and 38 cm diameters included iodine, CaCO3, adipose, and water samples. The dose (air kerma) was 14 mGy for all studies. The low and high energy CT data were simulated at 80 kVp and 140 kVp for DSCT, and in 20–58 keV and 59–120 keV energy ranges for PCCT, respectively. The experiments used Somatom Flash DSCT system and PCCT system based on photon counting CdZnTe detector with 2 × 256 pixel configuration and 1 × 1 mm2 pixels size. In simulated general CT images, PCCT provided higher contrast-to-noise ratio (CNR) than DSCT with 0.4/0.8 mm Sn filters. The PCCT with K-edge filter provided higher CNR than the PCCT with a Cu filter, and DSCT with 0.4 mm Sn filter provided higher CNR than the DSCT with a 0.8 mm Sn filter. In simulated DE subtracted images, CNR of the DSCT was comparable to the PCCT with a Cu filter. However, DE PCCT with Ho a K-edge filter provided 30–40% higher CNR than the DE DSCT with 0.4/0.8 mm Sn filters. The experimental PCCT provided higher CNR in general imaging compared to the DSCT. In experimental DE subtracted images, the DSCT provided higher CNR than the PCCT with a Cu filter. However, experimental CNR with DE PCCT with K-edge filter was 15% higher than in DE DSCT, which is less than 30–40% increase predicted by the simulation study. It is concluded that ideal PCCT can provide substantial advantages over ideal DSCT in CT imaging including DE subtracted CT. However, the limitations of the PCCT detector does not allow it to reach its full potential and therefore further efforts are needed to improve PCCT detectors.

Experimental study on the operating characteristics of a novel photovoltaic/thermal integrated dual-source heat pump water heating system

This paper proposed a novel solar photovoltaic/thermal (PV/T) integrated dual-source heat pump (DSHP) water heating system. This system used the circulating water in solar photovoltaic thermal system and air source to provide domestic hot water for domestic usage, and meanwhile decreased the cooling water temperature for the PV/T panel to improve the electrical conversion efficiency. An experimental PV/T integrated DSHP unit was established in Shanghai to examine its performance. The influences of the inlet temperature of the evaporator and the hot water temperature under water–water mode and the influence of the outdoor temperature under air–water mode on the system performance were studied. Energy analysis was conducted between water–water mode and air–water mode. The cooling effect and photovoltaic efficiency of the PV/T panel were evaluated. The results showed that when water side evaporator was used, the PV/T panel operating temperature can be decreased up to 45 °C, and the electrical conversion efficiency yielded a surplus of 10.3%.

European Association of Cardiovascular Imaging/Cardiovascular Imaging Department of the Brazilian Society of Cardiology recommendations for the use of cardiac imaging to assess and follow patients after heart transplantation.

European Association of Cardiovascular Imaging/Cardiovascular Imaging Department of the Brazilian Society of Cardiology recommendations for the use of cardiac imaging to assess and follow patients after heart transplantation.

Automated tube voltage selection in thoracoabdominal computed tomography at high pitch using a third-generation dual-source scanner: image quality and radiation dose performance.

The objective of this study was to evaluate the radiation dose and image quality performance of thoracoabdominal examinations with an automated tube voltage selection (tube voltage adaptation), tube current modulation, and high pitch using a third-generation dual-source computed tomography (CT) compared intraindividually with 120-kV examinations with tube current modulation with special attention on clinically relevant lesions in the liver, the lungs, and extrahepatic soft tissues. This study was approved by the institutional review board. Computed tomography of the body was performed using a third-generation dual-source system in 95 patients (mean body mass index, 25 kg/m²; range, 18-35 kg/m²). For 49 of these patients, all calculated tube settings and resulting dose values were recorded for each of the 12 gradual contrast weightings of the tube voltage adaptation algorithm. Spiral CT was performed for all patients with an intermediate weighting (grade 7) in a portal venous phase at 120 reference kV, 180 reference mAs, and pitch of 1.55. Objective image quality was assessed on the basis of contrast-to-noise ratio. Subjective image quality was assessed on the basis of clarity and sharpness of anatomical and pathological structures as well as interfering beam hardening and spiral and motion artifacts (heart, lungs, diaphragm). Previous examinations on a 64-slice scanner served as reference. All examinations were rated good or excellent for clinical diagnosis. Automated tube voltage selection resulted in significantly lower effective radiation dose (9.5 mSv) compared with the reference (12.0 mSv; P < 0.01). Contrast-to-noise ratio and image quality of soft tissue lesions were significantly increased (P < 0.01). Motion artifacts were significantly reduced (P < 0.01). Automated tube voltage adaptation combined with high-pitch protocols allows for a substantial radiation dose reduction while substantially increasing the image quality, even at large-volume exposure.

Perfusion computed tomography for detection of hepatocellular carcinoma in patients with liver cirrhosis.

To evaluate the diagnostic performance of dynamic perfusion CT (P-CT) for detection of hepatocellular carcinoma (HCC) in the cirrhotic liver. Twenty-six cirrhotic patients (19 men, aged 69 ± 10 years) with suspicion of HCC prospectively underwent P-CT of the liver using the 4D spiral-mode (100/80 kV; 150/175mAs/rot) of a dual-source system. Two readers assessed: (1) arterial liver-perfusion (ALP), portal-venous liver-perfusion (PLP) and hepatic perfusion-index (HPI) maps alone; and (2) side-by-side with maximum-intensity-projections of arterial time-points (art-MIP) for detection of HCC using histopathology and imaging follow-up as standard of reference. Another reader quantitatively assessed perfusion maps of detected lesions. A total of 48 HCCs in 21/26 (81%) patients with a mean size of 20 ± 10 mm were detected by histopathology (9/48, 19%) or imaging follow-up (39/48, 81%). Detection rates (Reader1/Reader2) of HPI maps and side-by-side analysis of HPI combined with arterial MIP were 92/88% and 98/96%, respectively. Positive-predictive values were 63/63% and 68/71%, respectively. A cut-off value of ≥85% HPI and ≥99% HPI yielded a sensitivity and specificity of 100%, respectively, for detection of HCC. P-CT shows a high sensitivity for detection of HCC in the cirrhotic liver. Quantitative assessment has the potential to reduce false-positive findings improving the specificity of HCC diagnosis. • Visual analysis of perfusion maps shows good sensitivity for detection of HCC. • Additional assessment of anatomical arterial MIPs further improves detection rates of HCC. • Quantitative perfusion analysis has the potential to reduce false-positive findings. • In cirrhotic livers, a hepatic-perfusion-index ≥ 9 9% might be specific for HCC.