Thermal performance of cold thermal energy storage system with fin and fin–foam structures

The heat transfer performance of most cold thermal energy storage (CTES) devices is limited by the low thermal conductivity of phase change materials (PCMs) and the increase in the thickness of PCMs. A comparative work was performed to explore the heat transfer performance of CTES systems with a fin structure (Fin-CTES) and a fin–foam structure (Fin–foam-CTES). The heat transfer performance, temperature distribution, and thermal effectiveness of Fin-CTES and Fin–foam-CTES at different inlet temperatures and volume flow rates of heat transfer fluid were investigated and compared. Results demonstrated that the overall heat transfer performance of Fin–foam-CTES is better than that of Fin-CTES. However, compared with the PCM in Fin-CTES, that in Fin–foam-CTES has a greater degree of supercooling, reaching 4.35 °C at the maximum. In the discharging (melting) process, Fin-CTES and Fin–foam-CTES have almost similar heat transfer effectiveness, in which the maximum difference is only 0.0107. That is, the enhanced heat transfer effect of the natural convection of the liquid PCM and the metal foam is basically the same during the discharging process.</p

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Ground-Motion Intensity Measures for the Seismic Response of the Roof-Isolated Large-Span Structure

Ground-motion intensity measures (IMs), which quantify and describe the characteristics of earthquake ground motion, are of utmost importance in the assessment of seismic risk and the design of resilient structures with large spans. The appropriate selection of a ground-motion IM is crucial in establishing a reliable and robust correlation between seismic hazards and structural demands. The current study presents a novel ground-motion IM that incorporates the influence of multiple vibration modes and period elongation resulting from isolation based on the velocity spectrum. A comprehensive study has been conducted to examine the efficiency of 37 different ground-motion IMs on a roof-isolated large-span structure with engineering demand parameters (EDPs), using far-field ground-motion data. The initial examination of the proposed intensity measure involves a planar lumped-mass model. Subsequently, a numerical model of a large-span roof-isolated structure, specifically the Beijing Workers’ Stadium, is constructed and examined. The results suggest that the proposed intensity measure (IM) demonstrates satisfactory adequacy and achieves optimal efficiency when considering three different engineering demand parameters among 37 other ground-motion intensity measures

Corrosion behavior of an AZ91D magnesium alloy under a heterogeneous electrolyte layer.

The corrosion behavior of an AZ91D magnesium alloy was investigated under a heterogeneous electrolyte layer by using electrochemical methods and surface analysis techniques. Dynamic polarization curves and morphological characterization were obtained at the center and near the edge zones under the electrolyte layer. The influence of the gas/liquid/solid three-phase boundary zone (TPB) on the corrosion behavior of the AZ91D magnesium alloy was discussed. The corrosion rate changed more significantly near the TPB zone than that at the other zones. The AZ91D alloy exhibited the characteristics of filiform corrosion together with shallow pitting corrosion. Different from the randomly distributed shallow pits, the filiform corrosion preferred to initiate near the TPB region and then progressively expanded adjacent to the edge of the electrolyte layer. The TPB zone played a vital role in determining the corrosion location, the corrosion morphologies and the corrosion rate of the magnesium alloy by influencing the mass transport process of carbon dioxide

How do city-specific factors affect migrant integration in China? A study based on a hierarchical linear model of migrants and cities.

BackgroundPrevious studies indicate that migrant integration is associated with migrants' characteristics as well as restrictions and opportunities in receiving cities. However, the effect of receiving cities and the relationship between migrants and receiving cities have not been fully explored due to the lack of large samples from cities. The objective of this study is to examine the effects of receiving cities alone and their regulating role in the interaction with individual characteristics.MethodsCross-city data on 154,044 Chinese domestic migrants above 15 years old in 289 cities from the 2017 China Migrants Dynamic Survey are used. Migrant integration is assessed by a four-dimensional model proposed by Esser, which is slightly adjusted according to the characteristics of Chinese migrants. A hierarchical linear model is used to measure the proportion of effects of city factors in migrant integration as well as the effects when city factors are considered alone and in interaction with individual factors.ResultsThe individual-level and city-level factors are responsible for 69.81% and 30.19% of the effect on migrant integration, respectively. City political factors do not affect migrant integration directly, and cities with larger sizes and higher wages can directly and significantly improve integration, while higher housing prices will directly inhibit integration. From the cross-level interaction of city and individual, different social, economic and political factors at the city level have an indirect impact on migrant integration by inhibiting or strengthening the effect of individual-level factors on migrant integration.ConclusionThis study is one of the first to show the effect of cities and the relationship between receiving cities and migrants on migrant integration by keeping the national context constant. It is necessary to weaken the social and economic privileges associated with a city's administrative level and reduce the negative impact of cities' social and economic conditions by implementing city agglomeration, developing advantageous industries and optimizing the industrial structure. It is also essential to improve migrants' socioeconomic capital through social support, occupation training and contiguous education

Capacitor Voltage Imbalance Mechanism and Balancing Control of MMC When Riding Through PTG Fault

Modular multilevel converter (MMC) based fault ride through (FRT) control is a promising solution to deal with the pole-to-ground (PTG) fault in high voltage direct current (HVDC) system. However, when MMC switches to the FRT control, capacitor voltage imbalance between upper and lower arms will occur, resulting in the deterioration of FRT performance. This letter provides a comprehensive analysis for the imbalance issue from the perspective of fundamental frequency circulating current (FFCC). It is found the imbalance during FRT stage will not expand continuously, but converge to a certain value gradually. The specific imbalance degree is closely associated with the amplitude of FFCC. In order to solve the imbalance issue, an open-loop balancing control is proposed. By introducing a fundamental frequency feedforward item to the inherent circulating current control, the proposed method can not only balance the capacitor voltages, but also minimize the amplitude of FFCC, and consequently the power loss of MMC during FRT process can be reduced. Finally, simulation results of PSCAD/ EMTDC verify the validity of theoretical analysis

Design, Synthesis and Cytotoxicity of Novel Dihydroartemisinin-Coumarin Hybrids via Click Chemistry

In order to develop novel chemotherapeutic agents with potent anticancer activities, we designed four series of novel compounds employing hybridization strategy. Twenty novel dihydroartemisinin-coumarin hybrids, 10a–e, 11a–e, 12a–e, 13a–e, were synthesized via click chemistry in this study and their structures were characterized by HRMS and NMR. The cytotoxic activities were measured by MTT assay against three cancer cell lines (HCT-116, MDA-MB-231, and HT-29) under normoxic or anoxic conditions, respectively. The target compounds exhibited moderate activity with IC50 values in the 0.05–125.40 μM range, and these compounds exhibited better activity against HT-29 cell line under anoxic condition. The cytotoxic activities of most compounds under anoxic condition displayed one- to 10-fold greater activity than under normoxic condition. Compounds 10a–e showed better selectivity against the HT-29 cell line than the other two cell lines. These results indicated that our design of CA IX inhibitors does correspond with its action mode to some degree and deserves further investigation

Application of Transthoracic Shear Wave Elastography in Evaluating Subpleural Pulmonary Lesions

Aim: The objective of this research was to investigate the feasibility of transthoracic shear wave elastography in the differentiation of subpleural masses. Methods: Between December 2019 and November 2020,82 consecutive patients with radiographic evidence (including chest X ray and thoracic computed tomography CT) of single subpleural lesion enrolled in this research. The Young’s modulus E (including Emean and Emax) of each lesion was detected, and the Young’s modulus E of malignant lesions were compared with those of benign ones. We made diagnoses according to the results of pathology or standard clinical course for at least 3 months. Receiver operating characteristic (ROC) analysis was plotted to determine the cut-off point by maximizing the Youden index. Results: The Emean and Emax of the benign and malignant group was 34.68 ± 12.12 kPa vs. 53.82 ± 11.95 kPa (p < 0.001), 57.77 ± 14.45 kPa vs. 76.62 ± 17.04 kPa (p < 0.001). The ROC of Emean showed that when the cut-off point was 43.8 kPa, the Youden index (0.53) for distinguishing benign and malignant tumors was the largest (sensitivity 80.4 %, specificity 72.2 %, AUC = 0.848, p < 0.0001). When the cut-off point recommended by Emax ROC was 73.5 kPa, the Youden index (0.44) for distinguishing benign and malignant tumors was the largest (sensitivity 76.1 %, specificity 66.7 %, AUC = 0.780, p < 0.0001). Conclusions: This study demonstrated that we can employ transthoracic shear wave elastography as a valuable instrument in differentiating benign subpleural lesions from malign ones

Improved Bayesian Optimization Framework for Inverse Thermal Conductivity Based on Transient Plane Source Method

In order to reduce the errors caused by the idealization of the conventional analytical model in the transient planar source (TPS) method, a finite element model that more closely represents the actual heat transfer process was constructed. The average error of the established model was controlled at below 1%, which was a significantly better result than for the analytical model, which had an average error of about 5%. Based on probabilistic optimization and heuristic optimization algorithms, an optimization model of the inverse heat transfer problem with partial thermal conductivity differential equation constraints was constructed. A Bayesian optimization algorithm with an adaptive initial population (BOAAIP) was proposed by analyzing the influencing factors of the Bayesian optimization algorithm upon inversion. The improved Bayesian optimization algorithm is not affected by the range and individuals of the initial population, and thus has better adaptability and stability. To further verify its superiority, the Bayesian optimization algorithm was compared with the genetic algorithm. The results show that the inversion accuracy of the two algorithms is around 3% when the thermal conductivity of the material is below 100 Wm−1K−1, and the calculation speed of the improved Bayesian optimization algorithm is three to four times faster than that of the genetic algorithm