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Cubic gauche polynitrogen (cg-N) is an attractive high-energy density material. However, high-pressure synthesized cg-N will decompose at low-pressure and cannot exist at ambient conditions. Here, the stabilities of cg-N surfaces with and without saturations at different pressures and temperatures are investigated systematically. Pristine surfaces at 0 GPa are very brittle and will decompose at 300 K, especially (1 1 0) surface will collapse completely just after structural relaxation, whereas the decompositions of surfaces can be suppressed by applying pressure, indicating that surface instability causes the cg-N decomposition at low-pressure. Due to the saturation of dangling bonds and transferring electrons to the surfaces, saturation with H can stabilize surfaces at ambient conditions, while OH saturation cannot because of getting electrons from the surfaces. An acidic environment or surface saturation with less electronegative adsorbates is more favorable for the stability of polymerized nitrogen., Comment: 21 pages, 5 figures

Recently, Lu-N-H materials were reported to have room-temperature superconductivity, and the Hubbard U correction on the Lu's $\textit{f}$-electrons is necessary, and a constant U = 5.5 eV was applied to different Lu-N-H configurations (Nature 615, 244 (2023)). Following simulations indicate that the superconducting transition temperature (T$_{c}$) of LuH$_{3}$ with U = 0 eV is 50 ~ 60 K, while the N-doped LuH$_{3}$ is below 30 K. Quite recently, calculations with U = 5 eV shows that the T$_{c}$ of N-doped LuH$_{3}$ exceeds 100 K. The properties of Lu-N-H are sensitive to the applied U values. Here, the structural and electronic Lu-N-H properties at high-pressure (0 ~ 10 GPa) are systematically investigated based on the hybrid functional. We show that different Lu-N-H configurations should possess different U values varying from 6.4 eV to 7.4 eV. Furthermore, at pressure ranging from 0 GPa to 1 GPa, the $\textit{f}$ and $\textit{d}$ band centers of N-doped LuH$_{3}$ show oscillation or even plateau, and the band gap of insulators also shows a platform near this pressure, this is consistent with the pressure range where room-temperature superconductivity appeared in Lu-N-H. Our work provides insights into the understanding of Lu-N-H materials and other hydrogen-rich superconductors based on the rare-earth elements.

The performance of H2O/EMISE (1-ethyl-3-methylimidazolium ethyl sulfate) absorption chiller driven by stationary solar collectors including the flat plate collector (FPC), evacuated tube collector (ETC), compound parabolic collector (CPC) in hot-humid climate is the focus of this study. As a case study, the cooling capacity of the absorption chiller is constant at 100 kW and used for air conditioning in Guangzhou, China with the inlet/outlet temperature of cooling water fixed at 32/37 oC and the inlet/outlet temperature of chilled water set at 17/12 oC. The effects of heat source temperature between 78-100 oC on the thermodynamic as well as economic performance of the solar absorption chiller system have been analyzed and meanwhile the application potentials of the three candidate solar collectors are compared also. The results show that there is an optimum heat source temperature makes the coefficient of performance (COP) and exergetic efficiency (ECOP) of solar absorption chiller system maximum, which is featured with a shifting to lower values compared to the optimum one that leads to the COP of absorption chiller machine maximum. Besides, while the CPC absorption chiller system has the best thermodynamic performance with the overall COP and ECOP about 0.351 and 0.027, respectively, the ETC system becomes the most economic one with the specific investment cost about 1194 USD/kW. Recommendations are given based on the findings as resources to help the design of solar driven H2O/EMISE absorption chiller systems in the hot-humid region.

Energy consumption of buildings accounts for more than 37.3% of total energy consumption while the proportion of energy-saving buildings is just 5% in China. In this paper, in order to save potential energy, the building envelope retrofitting is considered. An office building in Southern China was selected as a test example for energy consumption characteristics. The base building model was developed by TRNSYS software and validated against the recorded data from the field work in six days out of August-September in 2013. In addition, with a design of numerical simulation, sensitivity analysis was conducted for energy performance of building envelope retrofitting; six envelope parameters were analyzed for assessing the thermal responses. Results show that significant energy savings are obtained for the thermal transmittance (U-value) of exterior walls, infiltration rate, ventilation and shading coefficient, of which the sum relative sensitivity is about 91.06%. The results are evaluated in terms of energy and economic analysis. On the other hand, it appears that the cost-effective method improves the efficiency of investment management in building energy.

In modern life, emotions affect people in all aspects of their work and life. Long-term emotional problems tend to cause physical and mental problems such as depression. The photoplethysmogram(PPG) and electroencephalogram (EEG) etc are often used for emotion recognition, because the emotional state produces reactions from different biological systems of the human body. This article uses an internationally released emotional classification database called DEAP dataset that contains 32-channel standard EEG signals and 8-channel peripheral physiological signals. To achieve wearable emotion continuous recognition, this paper strives to obtain satisfactory emotion recognition through fewer EEG channels and peripheral physiological signals. Machine learning methods are used to classify arousal and valence that are often used in emotional recognition. The results show that the arousal classification accuracy can achieve 68% and the valence classification accuracy can achieve 66% with 5 channel EEG signal and one channel PPG signal, which can be monitored through a wearable headband.

With a constant-pressure mixing ejector, the performance characteristics of an ejector-expansion refrigeration cycle (EERC) using R1234yf as refrigerant have been investigated. Also, the performance of R1234yf and R134a in the EERC has been compared. The study shows that, at condensing temperature of 40 °C and evaporation temperature of 5 °C, the coefficient of performance (COP) and volumetric cooling capacity (VCC) of the R1234yf EERC peak up to 5.91 and 2590.76 kJ/m3, respectively. Compared with the standard refrigeration cycle the R1234yf EERC generally has a better performance, especially at the condition of higher condensing temperature and lower evaporation temperature. The COP and VCC improvements of the R1234yf EERC over the standard refrigeration cycle are also greater than that of the R134a cycle. In addition, the ejector design parameters including the pressure drop in suction nozzle, area ratio and component efficiencies on the R1234yf EERC performance have been analyzed.

In mass spectrometry based quantitative proteomics research, the emerging iTRAQ technique has been widely adopted for high throughput protein profiling, as it enables one to measure multiple samples simultaneously in one multiplex experiment and thus greatly enhances the throughput of protein quantification. However, the technical variation across different iTRAQ multiplex experiments is often large due to the dynamic nature of MS instruments. This leads to strong batch effects in the iTRAQ data. Moreover, the iTRAQ data often contain substantial batch-level non-ignorable missingness. Specifically, the abundance measures of a given protein/peptide are often missing altogether in all the samples from the same batch, with the missing probability depending on the combined batch-level abundances. We term this unique missing-data mechanism as the Batch-level Abundance-Dependent Missing-data mechanism (BADMM). We introduce a new method, mixEMM, for analyzing iTRAQ data with batch effects and batch-level non-ignorable missingness. The mixEMM method employs a linear mixed-effects model and explicitly models the batch effects and the BADMM in the likelihood function. With simulation studies, we showed that compared with existing approaches that utilize relative abundances and ignore the missing batches under the missing completely at random assumption, the mixEMM method achieves more accurate parameter estimation and inference.We applied the method to an iTRAQ proteomics data from a breast cancer study and identified phosphopeptides differentially expressed between different breast cancer subtypes. The method can be applied to general clustered data with cluster level non ignorable missing-data mechanisms., Comment: 23 pages, 3 figures

Eight models using only the sunshine duration for estimating the global solar radiation on a horizontal surface are evaluated at Changdu, Geer, Lasa and Naqu stations in Tibet, China against the measured meteorological data during 1994–2008. Based on statistical error tests, results show that the simple linear Angstrom–Prescott model is reasonably accurate in practice, and the modifications with complex expression are not necessary in Tibet. Then, two general Angstrom–Prescott models for estimating the daily and monthly average daily global solar radiation respectively in Tibet are proposed.

Solar radiation measurements are not easily available, especially for the diffuse solar radiation. In this study, two models for estimating the diffuse solar radiation are proposed based on multiple predictors including the clearness index, relative sunshine duration, ambient temperature and relative humidity. One of them aims to increase the estimation accuracy, and the other aims to estimate the diffuse solar radiation direct from other meteorological elements in the absence of the global solar radiation. For a case study, the performance of the proposed models is validated by comparing with eight existing models selected from literature against the measured data at Guangzhou station in China. Through the analysis based on statistical error tests, results show that the two models can estimate the monthly average daily diffuse solar radiation with good accuracy.

There are many solar constant values given and adopted by researchers, leading to confusion in estimating solar radiation. In this study, some solar constant values collected from literature for estimating solar radiation with the Angstrom–Prescott correlation are tested in China using the measured data between 1971 and 2000. According to the ranking method based on the t-statistic, a strategy to select the best solar constant value for estimating the monthly average daily global solar radiation with the Angstrom–Prescott correlation is proposed.

In this study, a new empirical model is proposed for estimating daily global solar radiation on a horizontal surface by the day of the year. The performance of the proposed model is validated by comparing with three trigonometric correlations at nine representative stations of China using statistical error tests such as the mean absolute percentage error (MAPE), mean absolute bias error (MABE), root mean square error (RMSE) and correlation coefficients (r). The results show that the new model provides better estimation and has good adaptability to highly variable weather conditions. Then the application of the methodology is performed for the other 70 meteorological stations across China.

In research of the copyright protection of digital text, according to the shortage of poor robustness and weakness of attack resistance for the existing text watermark, Chinese machine code and information gain strategy have been introduced into text zero-watermark scheme, which puts forward the text zero-watermark based on the Chinese Edit Distance, constructs the construction and detection process model, and designs the core algorithm. First, we introduce information gain to compute the weighting terms in paragraph to select the text feature. Then, we use Chinese machine code to express the text feature formally. Last, we compute the edit distance between the characteristic words in every paragraph and mark the commutation position to form an edit distance matrix to complete text zero-watermark construction. In detection stage, we analyze the edit distance and commutation position to reflect the distortion status. In order to validate effectiveness and feasibility of the scheme, simulation experiments are provided. The results indicated that the scheme has good robustness and strong ability against attack, especially, for the attack toward sentence type conversion and add & delete words, it has more obvious advantages.

By using the density functional theory (DFT) combined with the molecular dynamics (MD) simulations, structural and electronic properties of mono-vacancy (MV) defect in M��bius strip formed from graphene are investigated. Two kinds of MV are observed depending on the local structures around defects. At static condition, in the curved areas of M��bius strip, MV has the configuration of one pentagon and one nonagon ring (59-type), which is similar to that of carbon nanotubes and graphene. the most stable MV appear in the twisted areas and has a profile of two pentagon and two hexagon rings (5566-type) with one sp3 hybridized carbon at the central site. While DFT-MD simulations prove that the 5566-type MV is an unstable configuration at room temperature and will transform into a 59-type MV. Additionally, the melting behavior of graphene based M��bius strips are investigated through empirical potential MD simulations, and we find that their melting temperature is about 2750 K, which is lower than that of carbon nanotubes and graphene.