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To reduce the noise caused by the flow of refrigerant during the defrost cycle and preserve the ambient sound level, this study concentrated on exploring the mechanism of noise generation in the gas–liquid separator based on visualization experiments. A transparent gas–liquid separator made of quartz glass, which was instead of the original one, was fabricated to observe the flow pattern of refrigerant in the gas–liquid separator, and the relationship between flow pattern and noise generation was investigated. The results showed that the noise is mainly generated during the defrost cycle. The sound power level has a drastic fluctuation when the liquid level of refrigerant in the gas–liquid separator is higher than the outlet of the evaporation tube during the defrost cycle. The reduction in noise is achieved by the redesigns that prevent the liquid level of refrigerant in the gas–liquid separator being higher than the outlet of the evaporation tube during the defrost cycle. Then, the noise level of original design and two redesigns was measured in a high precision semi-anechoicroom, respectively. The noise level of the refrigerator reduces from 30.2 dB(A) to 26.1 dB(A) and 24.4 dB(A) by increasing the volume of the gas–liquid separator for 87.1% and installing a ball valve respectively.

We report a GLUTs/GSH cascade targeting-responsive bioprobe via the coordination of copper ions with a glucose-based coumarin derivative ligand for simple and ultrasensitive detection of circulating tumor cells.

In the residential air-conditioning system, the mal-distribution of the two-phase refrigerant deteriorates the performance of the multi-channel evaporator, especially in distributors. In this paper, the distribution uniformity and structural optimization of a type of air-conditioning distributor are investigated with simulation models and experiments. Two types of optimized distributors are proposed through the study on multiple structural factors, the Taguchi method and the summary of flow mechanism. Furthermore, the relevance between the mal-distribution and the performance of the evaporator is established by a heat exchanger design software. The results show that the distributor can alleviate the uneven phase distribution at the inlet through the following three effects: throttling of the orifice, diffusion and backflow in the cavity. Improvements are proposed based on these points, including enlarging the space of the mixing cavity and applying a hemispherical surface. It is confirmed that the optimized distributors have better performance compared to the original sample by simulation evaluations and experimental verifications. The non-uniformity index of optimized distributors reduced by 4.6% and 36.5%, respectively.

Constructing a fence for potential liquid hydrogen leakage is a common protective measure to prevent the unrestricted spread, and critically evaluating the effects of a fence is essential for the safe use of hydrogen energy. Based on NASA's large-scale experiment of liquid hydrogen release, a 3D numerical model considering the existence of fence is proposed to study the dynamic spread behaviors of hydrogen flammable cloud and liquid hydrogen pool. The results show that the liquid hydrogen pool keeps a downwind radius of about 1.75 m most of the time during the release, and the hydrogen flammable cloud has a limit spread distance. Three cases are set to comparatively evaluate the effect of the fence, which are full fence, downwind half fence and no fence. Under the three cases, liquid hydrogen pools all evaporate completely within 5 s. Full fence scenario has the modest spread scale of hydrogen flammable cloud in the atmosphere but the longest duration for 86 s, and the upwind fence causes an easily overlooked hazardous region due to the vortex here, thus constructing a full fence is not an ideal strategy when the spread direction is constant. Just constructing a downwind half fence leads to the greatest spread distance of the flammable hydrogen cloud, which are 33.6 m and 68 m in vertical and downwind directions. No fence case corresponds to the smallest diffusion scale of flammable hydrogen cloud in atmosphere but the longest near-ground spread distance for 43.35 m. Four stages can be divided to summarize the entire life period of the flammable cloud for the cases with and without a fence, while three stages for the case with a downwind half fence.

The vibration rectification error (VRE) of a pendulous accelerometer is a common problem in engineering applications. It is generally accepted that the accelerometer nonlinearity is the main cause of the VRE, but the nonlinearity reduction is a complicated procedure and is difficult to achieve. In this study, by analyzing the input and output relationship of an accelerometer, the pendulum deflection is also shown to be an important cause of the VRE both theoretically and experimentally. First, in order to ensure that the accelerometer pendulum moves in the linear region, thereby reducing the VRE, a theoretical model of the pendulum deflection angle is established. Next, the factors affecting the pendulum deflection angle are analyzed, and the relationship between the correction network parameters and the pendulum deflection angle is calculated and simulated. To validate the proposed method further, a fixed-frequency vibration experiment is carried out. The pendulum deflection angle and the VRE are physically measured, and the obtained results are consistent with the simulated ones. Further, random vibration experiments simulating real environments are carried out. The results show that with decreasing pendulum deflection angle, the frequency corresponding to the maximum pendulum deflection angle increases, and the VRE decreases. In conclusion, the performed pendulum deflection angle simulation, pendulum deflection angle measurement, and VRE measurement for pendulous accelerometers have a strong correspondence and are easy-to-implement and accurate methods for VRE analysis. In addition, we believe that this procedure can be extended to the study of similar instruments with moving parts.

Background We evaluated the application value of copy number variation sequencing (CNV-seq) to analyze chromosomal abnormalities in products of conception (POCs) from first- and second- trimester miscarriages. Methods Approximately 650 POCs from spontaneous abortion were collected from April 2018 to May 2020. CNV-seq and QF-PCR were performed to determine the characteristics and frequencies of copy number variants (CNVs) with clinical significance. Clinical features were recorded. Results Clinically significant chromosomal abnormalities were identified in 355 (54.6%) POCs, including 217 (33.4%) autosomal trisomies, 42(6.5%) chromosomal monosomy and 40 (6.2%) pathogenic CNVs (pCNVs). Chromosomal trisomy mainly occurred on chromosomes 16, 22, 21, 18, and 15. Gestational week was a negative correlative factor for chromosome abnormality.Maternal age was the positive correlative factor of chromosome abnormality. However the occurrence of monosomy X was not related to maternal or gestational age. The frequency of chromosomal abnormalities in women with a normal live birth history was 55.3%, vs 54.4% in women without a normal live birth history (P > 0.05). There were no significant differences among women without, with 1, and ≥ 2 previous miscarriages history regarding the rate of chromosomal abnormalities (P > 0.05); CNVs were less frequently detected in women with advanced maternal age than in women aged ≤ 29 years and 30–34 years (P

Most phase change materials employed in latent heat thermal energy storage suffer from poor thermal conductivity both in liquid and solid phases, leading to low heat transfer effectiveness. To overcome this limitation, multiple PCMs and gradient copper foam have been used to accelerate the melting of phase change materials and improve the heat transfer effectiveness. The heat transfer performance of shell-and-tube thermal energy storage unit consisting of radial multiple PCMs and single PCM was numerically investigated. The utilization of single PCM showed better heat transfer effectiveness compared to that using radial multiple PCMs. The time saving for complete melting was up to 87.5%. The results implied that the radial multiple PCMs have no advantage in thermal storage compared to single PCM. Based on single PCM system, three types of gradients of copper foam, named positive gradient, non-gradient and negative gradient were designed in this study. The results indicated that the negative gradient type offers better heat transfer effectiveness than the non-gradient and positive gradient types. However, the temperature distribution of non-gradient type was more uniform compared to positive and negative types. Besides, an optimal configuration 0.99–0.97-0.89 of negative gradient was recommended to further reduce the complete melting time by 23.7%.

The experimentally known reaction of Cp2Cr2(CO)6 with white phosphorus (P4) to give CpCr(CO)2(η3-P3), Cp2Cr2(CO)4(μ-η,2η2-P2), and the triple-decker sandwich Cp2Cr2(μ-η,5η5-P5) is of interest since the P4 reactant having a tetrahedral cluster of four phosphorus atoms is converted to products having P2, P3, and P5 ligands. The mechanism of this obviously complicated reaction can be dissected into three stages using a coupled cluster theoretical method that has been benchmarked with the P2, Mn(CO)5, and CpCr(CO)3 dimerization processes. The first stage of the Cp2Cr2(CO)6/P4 reaction mechanism generates the unsaturated singlet intermediate Cp2Cr2(CO)5 that combines with the P4 reactant. Decarbonylation of the resulting Cp2Cr2(CO)5(P4) complex provides a singlet tetracarbonyl readily fragmenting into the stable triphosphacyclopropenyl complex CpCr(CO)2(η3-P3) and the chromium phosphide CpCr(CO)2(P). The isomeric triplet tetracarbonyl Cp2Cr2(CO)4(P4), readily fragments into CpCr(CO)2(η2-P2), which can generate the stable diphosphaacetylene complex Cp2Cr2(CO)4(η,2η2-P2) as well as the pentamer [CpCr(CO)2]5(P10). Combination of the coordinately unsaturated CpCr(CO)(η3-P3) with CpCr(CO)2(η2-P2) can lead to a ring expansion. This generates the P5 pentagonal ligand in a Cp2Cr2(CO)3(P5) precursor to the experimentally observed carbonyl-free triple-decker sandwich Cp2Cr2(μ-η,5η5-P5) after three successive decarbonylations.

There is a shortage of research in the literature on the evaporation rate of the liquid pool under instantaneous conditions, which is important for the risk assessment of the liquid hazard leakage accidents. Previous perfect thermal contact model and typical pool boiling could not completely represent the boiling process in the spreading liquid pool. In this work, the spreading liquid pool was characterized as a free-surface jet impingement on the plate surface. Liquid nitrogen (LN2) was adopted to simulate liquid hydrogen (LH2) and liquid natural gas (LNG) leakage, and a series of transient jet impingement boiling experiments were conducted on the concrete surface. Liquid jetted upon the stagnation region, and the transient heat flux from the concrete surface was estimated by transfer function method. The boiling curve obtained in the present study appears significantly different from the typical pool boiling, which indicate that large deviation will occur when the typical pool boiling correlations are used for instantaneous leakage, at least for the stagnation region. A point between the onset of nucleate boiling point and fully developed nucleate boiling point was recognized, which represents the turn of forced convection dominated to nucleate boiling dominated. It is confirmed that the heat transfer was enhanced with increased jet height z, and the peak values were found at z/d = 8.

The potential hazard of liquid hydrogen is still a problem for hydrogen-energy-driven automobile application. Based on the previous multicomponent-phase-change modeling of cryogenic and combustible liquids leakage. This paper has developed three different physical models to simulate the evaporation and dispersion processes of the liquid hydrogen (as vehicle fuel) that is leaking in open area, garage and tunnel scenarios. The leakage liquid hydrogen is 5.6 kg with a horizontal release direction on the ground. Cloud shape, duration time and hazard ranges are analyzed during the period of hydrogen cloud growing and shrinking in different environments. The results indicate that the case in open area displays the greatest flammable cloud volume among these three scenarios with 1133 m3 in ignition hazard and 356 m3 in detonation hazard, but the cloud mainly disperses above the height of 1.5 m, and it lasts for the shortest duration. Therefore, it would relatively safer than other two scenarios. The garage scenario has the longest dispersion duration time of 83.4 s for ignition and 30 s for detonation, and the widespread hazard ranges can put threat to all cars in the garage. The tunnel case shows the maximum downwind hazard distances below the height of 1.5 m. The corresponding ignition and detonation distances are 26.8 m and 24.4 m.

In this paper, we proposed a theoretical model to study the dispersion of hydrogen. The model given a correlation between the concentration and temperature for cryogenic gases. The model based on adiabatic mixing hypothesis and neglected exterior heat sources, and thought the gas mixture was always at quasi-steady state. Real-gas law was adopted, and thermal physical properties of the gases are obtained from NIST REFPROP database. The concentration curve approximately appears a decreasing straight line, and turns on dew point and ice point, since heat released from water vapor phase change. Compared with liquid hydrogen and liquid natural gas spill experimental data, the model obtained well agreement solutions. Effects of three typical weather conditions (atmospheric temperature, relative humidity and barometric pressure) on hydrogen dispersion were quantitatively studied. It is confirmed that the dispersion is excited in summer, and is depressed in winter and transition seasons with increased ambient temperature. With increased ambient temperature, the effect of increased enthalpy reduction of the dry air components and the effect of the water latent heat are respectively dominate in the 268.15–293.15 K and 293.15–308.15 K ranges. Compared to ambient temperature and barometric pressure, relative humidity has the strongest positive effect on hydrogen dispersion, and the slight dampening effect of barometric pressure could be neglected.

The physical/probabilistic meanings of fractional derivatives or integrals are very basic and important problems in fractional calculus. In this paper, we investigate the probabilistic interpretations of the general fractional derivatives with memory effect and their connections with cut-off distributions. Some examples like the cut-off Rayleigh distribution and the Atangana–Gómez fractional derivative are especially discussed. This paper shows that the kernels of the general fractional derivatives with memory effect may be not the same as the density functions of the physical processes described. For example, the kernel of Atangana–Gómez fractional derivative is a Gaussian function but its corresponding probabilistic distribution is a cut-off Rayleigh distribution.