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With the wide application of information technologies such as big data, the Internet of Things, and cloud computing, college students have accumulated a large amount of personal information and daily behavior data in their daily studies and life. How to dynamically integrate multidimensional information of students to build accurate student portraits, using multi-indicator data of student behavior and comment texts, and finding out students with abnormal behavior from among many students has become an important problem to be solved. This paper proposes an abnormal behavior prediction method integrating multiple indicators of student behavior and text information (ABPM-IMISBTI) for the problem of abnormal behavior prediction of college students in the big data environment. First, given the problems of multidimensionality, timeliness, and dynamics of student behavior information fusion in the construction of student behavior portraits, by integrating students’ objective tags and subjective tags, an optimized K-means algorithm based on a cloud platform environment is proposed. Second, aiming at the problem of insufficient text information analysis in the analysis of students’ abnormal behavior, the ABPM-IMISBTI method is proposed to solve the prediction of students’ abnormal behavior through long and short-term memory networks (LSTM) combined with student behavior multi-index data and text information. Finally, this paper takes student achievement prediction as an example for verification. The experimental results show that, compared with other prediction methods, the ABPM-IMISBTI method proposed in this paper can improve the accuracy of student behavior prediction, and then quickly determine the abnormal behavior of students, to improve the level of education management in universities and promote the development of safe campuses, smart campuses, and smart education.

In order to carry out an in-depth study of the differences in the molecular structure evolution of the vitrinite and the inertinite during coalification, the chemical structure of 13 groups of vitrinite and inertinite with different coal ranks were comprehensively characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and 13C nuclear magnetic resonance (13C NMR). The correlation of structure parameters and vitrinite random reflectance (Ro, ran) were analyzed. The results show that three evolution stages of vitrinite were observed with Ro, ran at 0.35%–0.90%, 1.20%–2.67%, and 3.03%–4.20%, and two evolution stages of inertinite were marked with Ro, ran at 0.35%–2.07% and 2.07%–4.20%. The fa, DOC, I, fa', faH, faN, faB, Xb, La, Lc, and Nave of inertinite are always larger than vitrinite, whereas the A(CH2)/(CH3), fal, fal*, falH, d002 of inertinite are always smaller than vitrinite. When Ro, ran = 0.35%–0.90%, the oxygen-containing functional groups and aliphatic structure of vitrinite fall off rapidly, the condensation degrees of the aromatic ring, La, Lc, and Nave increase, whereas the lengths of side chains and d002 decrease. When Ro, ran = 1.20%–2.67%, the vitrinite structure variation follows the same trend as the first stage, but the evolution rate is significantly lower. When Ro, ran = 0.35%–2.07%, the oxygen-containing functional groups, methyl groups, and methylene groups of inertinite fall off at a slower rate than those of vitrinite. The aromaticity, condensation degree, aromatic carbon content, and order degree of microcrystalline structure also increase at a rate less than that of vitrinite. The vitrinite and inertinite structure variation becomes flat, and the structures of both macerals are similar in the high metamorphic stage. The content of oxygen-containing functional groups and aliphatic chain length decrease to the lowest, whereas the aromaticity increases to the maximum. This study contributes to a comprehensive understanding of the chemical structure differences between vitrinite and inertinite, which can provide a theoretical reference for the clean utilization of coal and coalbed methane (CBM) exploration and development.

To study the possible adverse impacts of urbanization on the accumulation of heavy metals in cultivated soils. Five hundred thirty-one topsoil samples in the farmland of the peripheral areas of western Ningbo City, Zhejiang Province, Southeast China, were collected. The contents of heavy metal elements, As, Cd, Cr, Cu, Hg, Ni, Pb, Zn, and crustal stable trace elements, Li, Eu, Sc, Sm, in the samples were determined. The stable trace elements, best correlated with the heavy metals, were chosen as the reference elements to calculate the Environmental Geochemical Baselines (EGBs) of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the soils. Based on the established EGBs, the Enrichment Factors (EF) and Hankson Potential Ecological Risk (HRER) of the heavy metals in the soils were calculated to assess their potential ecological hazard risks. As a result, more than 30% of the sampling points of the study area were in moderate, considerable, or high risk of Cd, and 42% in moderate or considerable risk of Hg. The other heavy metals in the soils were mostly in low ecological risk. The BAF (Bio-accumulation Factor) and RAC (Risk Assessment Code) of Cd in the Cd high-risk soils were 12.43% and 45.14% on average, respectively, suggesting its high bio-availability. About 80% of the rice grain growing on the Cd high-risk soils of the study area exceeded the threshold of Cd for food safety, indicating high edible risk. It implies that the farmland of the study area has been significantly adversely impacted by industrial, vehicular, or other anthropogenic activities.

The physical properties of thick coal seams show strong vertical heterogeneity; thus, an accurate characterization of their pore structure is essential for coalbed methane (CBM) exploration and production. A total of 18 coal samples, collected from a thick coal seam in the Yili Basin of NW China, were tested by a series of laboratory experiments to investigate the peat mire evolution and pore structure characteristics. The results show that the No. 4 coal seam has undergone multiple stages of evolution in the peatification stage, and was divided into four water-transgression/water-regression cycles according to the regular cyclic changes of the vitrinite/inertinite ratio, structure preservation index, gelification index, vegetation index, trace element ratios, and stable carbon isotopes of organic matter. The changes of pore structure characteristics with the changes of coal deposition cycles are also analyzed. It is concluded that pore structure characteristics of the four cycles are quite different. In each water-transgression cycle, the vitrinite gradually increased and the inertinite gradually decreased, resulting in a decrease of the porosity, pore volume, specific surface area, and fractal dimension. While in each water-regression cycle, the vitrinite gradually decreased and the inertinite gradually increased, leading to an increase of the porosity, pore volume, specific surface area, and fractal dimension. A strong relationship exists between the porosity, pore volume, specific surface area, fractal dimension, and submacerals, with fusinite and semifusinite which contained more pores having a positive correlation, desmocollinite and corpovitrinite which contained few pores having a negative correlation.

An accurate understanding of molecular structure evolution during pyrolysis is essential for the clean utilization of coal. In this study, middle-rank coal was taken as the research subject, and vitrinite and inertinite samples were stripped from coal using a hand picking and sink–float separation process. In situ Fourier transform infrared (FTIR) spectroscopy and in situ X-ray diffraction (XRD) were performed to compare the macromolecular structure changes between vitrinite and inertinite during pyrolysis. The results show that the aromaticity (I), the polycondensation degree of aromatic rings (DOC), the average lateral sizes (La) of basic structure unit (BSU), and the stacking heights (Lc) of BSU in both vitrinite and inertinite during pyrolysis increase continuously with increasing temperature. The values of these parameters for inertinite are higher than those of vitrinite, suggesting that the aromatization degree of inertinite has always been higher than that of vitrinite. In situ FTIR spectroscopy shows that the macromolecular structure evolution of vitrinite and inertinite could be divided into three stages based on temperature: 30–200 °C, 200–300 °C, and 300–500 °C. The content of C–O–C, aromatic C=O, O–H groups, and aromatic ring C=C gradually decreases, while that of the CH2 in aliphatic hydrocarbons increases between 30 °C and 200 °C. The 200–300 °C stage is mainly filled by the synergistic effects of aliphatic and aromatic groups. The content of aliphatic groups, C–O–C groups, aromatic C=O, and aromatic ring C=C of both vitrinite and inertinite decreases greatly. The 300–500 °C stage is dominated by the aromatization and condensation of macromolecules. The substituents of the aromatic system gradually detach, leading to an increase in I and DOC. From 30 °C to 1000 °C, in situ XRD results reveal a difference in macromolecular structural evolution between vitrinite and inertinite. The arrangement of aromatic layers in vitrinite tends to be ordered during pyrolysis, whereas there are no significant changes in the inertinite. However, the aromatic layers of inertinite are always more compact than that of vitrinite. In addition, the aliphatic side chains of inertinite are more stable than that of vitrinite during the pyrolysis process.

Coalbed methane (CBM) development in the southern Junggar Basin of Northwest China has aroused extensive attention owing to its significant resource potential. The accurate characterization of coal pore structure is important for CBM exploration and production. In order to explore the relationship between coal pore structure and macrolithotype, which has rarely been studied in the southern Junggar Basin, a series of laboratory experiments were performed on eight samples of different macrolithotypes. The results show that the porosity exhibits regularity with macrolithotype in the order bright inertinite > liptinite. Finally, according to the research results, the reservoir fracturing improvement should be more arranged on the dull or semi-dull coals, and the producing layers should be bright or semi-bright coals as much as possible on the premise that the gas contents of coal layers are not much different from each other.

Solid fines generation in coalbed methane (CBM) development can cause serious formation damage and production breakdown. The anisotropy of coal reservoirs makes fines issue more complicated. In this study, the experimental analysis of the correlation between tectonically deformed coal types and fines generation characteristics was implemented. Two samples with different coal structure types, undeformed coal and granulated coal, were collected from the same coal seam. Under single-phase fluid flow, two sets of core flooding experiments were conducted to generate fines from these samples. The yields of fines produced at varying experimental conditions were analyzed quantitatively. The characteristics of these fines were microscopically observed through the use of a laser particle size analyzer, a scanning electron microscope, and a polarizing microscope. The results indicated that tectonically deformed coal types significantly influenced the generating intensities, particle sizes and morphological features of fines. Because of the varying degrees of structural destruction, compared with undeformed coal, granulated coal contained more original tiny fines in the fractures and was more sensitive to variations of fluid flow rates and reservoir effective stress, which could intensify the generation of fines. Undeformed coal could generate fines with wider particle-size distribution ranges and larger mean particle sizes than granulated coal could. The micromorphology of fines produced from undeformed coal was mainly angular. However, for granulated coal, most of the fines were subangular and even subrounded. No appreciable impact of the development of tectonically deformed coal on the compositions of fines was found. Because of the water sensitivity of clay minerals and the stress sensitivity of vitrinite, the produced fines contained more clay minerals and vitrinite with increases of displacement velocities and confining pressures under laboratory conditions. Through well logging interpretation, the development intensity of tectonically deformed coal in three CBM wells was identified. After analysis of the concentration and mean particle size of fines collected from these wells, it was concluded that the more developed the tectonically deformed coal, the higher the fines concentrations and the smaller the fines mean particle sizes, which was consistent with the experimental results.

In order to study the evolution of the mechanical properties and macromolecular structures in different macerals of tectonically deformed coal (TDC), vitrinite and inertinite samples were handpicked from six block TDCs in the same coal seam with an increasing deformation degree (unaltered, cataclastic, porphyroclast, scaly and powdery coal). The micro mechanical properties were tested by the nanoindentation experiment and the macromolecular structures were measured using 13C nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). The results show that the range of hardness and elastic modulus of inertinite is 0.373–1.517 GPa and 4.339–12.158 GPa, respectively, which is significantly higher than that of vitrinite with values of 0.278–0.456 GPa and 4.857–7.810 GPa, respectively. From unaltered coal to powdery coal, the hardness of vitrinite and inertinite gradually decreases, with the difference between these macerals becomes smaller and the elastic modulus of vitrinite shows an increasing trend, while that of inertinite was more variable. Both the NMR and FITR results reveal that the macromolecular structure of inertinite has similar structural transitions as vitrinite. As the degree of deformation increases, the aliphatic side chains become shorter and the aromaticity is increasing. Macromolecular alterations caused by tectonic stress is expected to produce defects in the TDCs, therefore there should be more interspacing among the macromolecular groups for the extrusion of macromolecules caused by the indenter of the nanoindentation experiment, thereby reducing the hardness. The elastic modulus of coal is believed to be related to intermolecular forces, which are positively correlated to the dipole moment. By calculating the dipole moments of the typical aromatic molecular structures with aliphatic side chains, the detachment of the aliphatic side chains and the growth of benzene rings can both increase the dipole moment, which can promote elastic modulus. In addition, the increasing number of benzene rings can create more π-π bonds between the molecules, which can lead to an increase in the intermolecular forces, further increasing the elastic modulus.

In order to study the trace element enrichment mechanism, this paper reports new petrology, geochemistry, and mineralogy data on the Permian coals of the Junger mining district and the Hebaopian mining district, northeastern Ordos Basin. In comparison with hard coals worldwide, the P2s1 coals are enriched in Be and the P1t3 coals are enriched in Zr in the Junger mining district, while the P2s1 coals in the Hebaopian mining district are enriched in Li, Zr, and Hf. The provenances of the enriched elements in the Permian coals from the Junger and Hebaopian mining districts are the Middle Proterozoic moyite in the Yinshan Oldland and the Benxi Formation bauxite. The paleopeat-forming environments of the Junger-Hebaopian mining district, northeastern Ordos Basin, were reconstructed in detail using the nature of the macerals, geochemical indicators, and mineralogical characteristics, with special emphasis given to the key role of paleopeat-forming environments in Ga, Li, and REY enrichment by comparing the variations in the Ga, Li, and REY contents to the paleopeat-forming environment characteristics. In the Junger-Hebaopian mining district, the higher REY concentrations mainly occur in coals derived from Neuropteris and Lepidodendron, and the coals formed in relatively alkaline, suboxic to anoxic, brackish or seawater influenced environments with strong hydrodynamics, while Li enrichment occurs in coals formed from sphenopsids and formed in acidic, brackish water influenced, relatively anoxic environments with strong hydrodynamic conditions. In addition, an acidic, freshwater, suboxic sedimentary environment with weak hydrodynamic conditions and Neuropteris and Lepidodendron peat-forming vegetation is beneficial to the enrichment and accumulation of Ga and REY. Although there is no direct evidence to support this hypothesis, a sequence of events that could have influenced the trace-element contents of the studied coals is proposed based on the general trace-element geochemistry of paleopeat-forming environments. This theory provides valuable insight into the selection of appropriate mining targets for these beneficial metal mineral resources (Ga-Li-REY) in other coal-bearing basins.

The different responses of vitrinite and inertinite to thermal metamorphism strongly affect the evolution of nanopores in different macerals of coal reservoirs. In order to reveal these differences during coalification, vitrinite and inertinite samples were handpicked from 10 block coal samples. A series of laboratory experiments were performed to explore the macromolecular structure and nanopores of the samples. The results indicate that the nanopore structure of the vitrinite showed obvious regularities with the reflectance of vitrinite (in oil, Ro), but that of the inertinite did not. The macromolecular structure of the inertinite did not correlate with Ro, whereas the vitrinite showed obvious correlations with Ro. Therefore, the nanopore structure of the inertinite cannot be affected by changes in Ro. The nanopore structures of both the vitrinite and inertinite were affected by the changes of macromolecular structures. The detachment of the aliphatic side chains and the promotion of the aromatic degree and the aromatic ring polycondensation degree decreased the micropore surface area (micro-SA) because the longer aliphatic side chains and lower degree of aromatic ring polycondensation make the surface of the coal particle more heterogeneous. The increases in the aromatic degree and aromatic ring polycondensation degree increased the mesopore volume (Vmes), total pore volume excluding micropores (VT), mesopore surface area (meso-SA), and Brunauer–Emmett–Teller (BET) specific surface area (BET-SA) because more isolated pores were connected with each other; thus, more interspace emerged among the aromatic ring layers with an increase in Ro. However, this does not mean that these regularities of inertinite are related to the coal rank, because macromolecular structures of the inertinite had been fixed prior to the coal formation and is not sensitive to coalification. These results are expected to enhance the understanding of the differences in vitrinite and inertinite nanopore structure evolution that occurs during coalification.

Hydraulic fracturing is an effective way to improve the productivity of coalbed methane (CBM). But fines intrusion into fracturing proppant can result serious permeability change and gas productivity reduction. The effects of fines particle size and the inorganic mineral content of fines on fines migration and permeability changes in the proppant were investigated by physical simulation and experiments on coal and mudstone samples from the Hancheng block in the Eastern Ordos Basin. Based on analyzing the characteristics of output fines mass, size distribution, micro-morphology and mineralogy, the regularities of fines migration and the permeability affected by fines particle size and inorganic mineral content of fines were revealed. The results show that the output fines mass increases while the decreasing of the particle size of the injected fines and the inorganic mineral content of injected fines. The particle sizes of fines output get smaller with the increase of the flow velocity and the inorganic mineral content. The permeable capability of the proppant channel is influenced by particle size and inorganic mineral content as follows: (1) Proppant channels with fines of 63–125 μm in particle size show lower permeability during water injection than the other two groups of

Circulating fluidized bed combustion (CFBC) ash can be used as supplementary cementitious material for concrete production for its high pozzolanic activity. We investigated the effect of curing conditions on the hydration and performance of CFBC ash-Portland cement system (30: 70, by mass) including hydration products, paste microstructure, linear expansion ratio, chemically combined water content and compressive strength. The results show that tobermorite rather than ettringite is generated under the condition of autoclaved curing. The expansion and mortar strength of the system cured in water is higher than those cured in air at a given age, and the strength and bulk volume may retract under the condition of air curing. In addition, autoclaved curing facilitates the increase of strength gain at early curing ages (the increase rate lowers down in the following ages) and the improvement of system volume stability. It is suggested that sufficient water is necessary for the curing of CFBC ash cementitious system, and autoclaved curing may be considered where volume stability is a primary concern.

Pulverized coal is one of the main controlling factors constraining the capacity of coal-bed methane wells during CBM drainage. The characteristics of pulverized coal can be used to identify the sources of the pulverized coal particles and to develop reasonable means of controlling pulverized coal output. Using light transmission microscopy, laser particle size testing, X-ray diffraction, reflection polarized optical microscopy, and scanning electron microscopy with energy dispersive X, the characteristics of pulverized coal collected during CBM drainage in the Hancheng block were analyzed for concentration, particle size, composition, and morphology. These traits were used to identify the sources of pulverized coal. The results showed that coal body structure (structural damage) was a primary control factor of pulverized coal output. The sizes of the pulverized coal particles tended to be around 100 μm. The main components of pulverized coal were vitrinite and clay minerals. The pulverized coals were divided into groups based on their columnar, flaky, or granular morphology. Columnar pulverized coal may involve the formation of the native structure coal or the fragmented coal that later sustains erosive damage. Flaky pulverized coal may be produced by the flaking of scaled coal or leaf coal. In this way, granular pulverized coal may be produced from granulated coal. Therefore, the morphology of the pulverized coal was found to be related to its coal body structure and to late mechanical destruction.

This paper puts forward the concept of exploration types and exploration models that can be used to find coal deposits. These were developed by taking into account the complexity and spatial differences of geological and geographical conditions of China's coalfield. ‘Exploration types’ here refers to groups of coal deposits similar in terms of the basic features of occurrence of the coal seams and the degree of difficulty of the exploration. ‘Exploration models’ here refers to generalizations and summations of advantageous geological conditions, effective technical exploration methods, and sound exploration programs and layout schemes suitable to different exploration types on the basis of the regularity of the occurrence of coal. Depending upon several factors that determine the degree of difficulty of exploration, such as regional geological conditions, the physical geographic environment, and the level of geological prospecting work performed, exploration for coal deposits can be divided into four types: (1) areas beneath and peripheral to old and existing coal mining zones in eastern China; (2) areas hidden by huge thick Cenozoic cover in eastern and central China; (3) geologically complex areas in eastern and southern China; and (4) geographically and geomorphologically complex areas in western China. In view of the different purposes and tasks involved in exploration, exploration models that are suited to different exploration types have been established, including the application of exploration methods, arrangement of exploration programs, and exploration engineering techniques. New exploration types and models promote the scientific and systematic features of coal geological exploratory engineering.

Twin kHz quasi-periodic oscillations (QPOs) have been found in the emission spectra of about thirty X-ray neuron star systems, where the upper ones of twin QPOs are often interpreted as the Keplerian frequencies of the accreting matter orbiting around the central stars. The observations of the kHz QPOs can be used to constrain the masses of neutron stars (NSs), and in particular to imply the properties of the matters at nuclear densities. By the way, we discuss the preferences of some kHz QPO models that constrain the NS parameters.

The spatial distributions of old neutron stars (NSs) with ages 109 to 1010 yr in our Galaxy are investigated byMonte Carlo simulation under two different initial random velocity models. It is found that the scale heights of the distribution increase with the Galactic radial distance. The location of the peak of the NS distribution is closer to the Galactic center than that of their progenitors. The results from our detailed numerical analysis reveal that there is resemblance between the simulated old NS distribution and the structure of the observed HI disk.

In the presence of dense multipath, the threshold-based time of arrival (TOA) estimation methods have attracted interest for node localization in ultra-wideband (UWB) wireless sensor networks (WSNs). Since the first arrival path is not always the strongest one in many actual situations, we propose to determine the real TOA using the constant false alarm rate (CFAR) detector method. Unlike conventional Gaussian or Rayleigh background, we assume the amplitude of the observal noise to be Weibull distributed. Given the probability of false alarm, the threshold of TOA detector is derived based on Weibull distribution function. Using the obtained TOA values, the multilateral localization is employed to compute the positions of nodes. The three-dimensional (3D) Taylor algorithm is given to solve the non-linear equations. The simulations prove that the proposed method has high time-resolution and low computational load in positioning of WSN nodes under Weibull noise and dense multipath.

This paper investigates the problem of estimating multiple parameters for large multi-input multi-output (MIMO) radar system in the situation that the numbers of the transmitter and receiver sensors are large that the number of samples could not satisfy the request to confirm that the population covariance matrix would be replaced by the sample covariance matrix. To obtain high-resolution in spatially close angle estimation for multi-target, multiple electromagnetic vector sensors at the receiver are equipped. A novel random matrix theory (RMT) based approach is proposed to joint estimate the direction-of-departure (DOD), direction-of-arrival (DOA) and two polarization parameters based on two 2D G-MUSIC algorithms. The estimation performance of this paper outperforms that of the conventional algorithms since it has the ability to estimate the parameters more exactly when the number of samples is not sufficient compared with the numbers of the transmitter and receiver sensors. In addition, the exploit of polarization diversity has improved the resolution especially when two or more targets are too close to be distinguished. The simulation results validate the better performance of the proposed method compared with that of the conventional MUSIC algorithm.

Based the Alfven wave oscillation model (AWOM) and relativistic precession model (RPM) for twin kHz QPOs, we estimate the emission positions of most detected kHz QPOs to be at r=18+-3 km (R/15km) except Cir X-1 at r = 30\+-5 km (R/15km). For the proposed Keplerian frequency as an upper limit to kHz QPO, the spin effects in Kerr Spacetime are discussed, which have about a 5% (2%) modification for that of the Schwarzchild case for the spin frequency of 1000 (400) Hz.The application to the four typical QPO sources, Cir X-1, Sco X-1, SAX J1808.4-3658 and XTE 1807-294, is mentioned., Comment: Science China, Physics, Mechanics & Astronomy, 2010, 53, NO.1

In this paper we investigate the space and velocity distributions of old neutron stars (aged 109 to 1010 yr) in our Galaxy. Galactic old Neutron Stars (NSs) population fills a torus-like area extending to a few tens kiloparsecs above the galactic plane. The initial velocity distribution of NSs is not well known, in this work we adopt a three component initial distribution, as given by the contribution of kick velocities, circular velocities and Maxwellian velocities. For the spatial initial distribution we use a Gamma function. We then use Monte Carlo simulations to follow the evolution of the NSs under the influence of the Paczy{\P}nski Galactic gravitational potential. Our calculations show that NS orbits have a very large Galactic radial expansion and that their radial distribution peak is quite close to their progenitors' one. We also study the NS vertical distribution and find that it can well be described by a double exponential low. Finally, we investigate the correlation of the vertical and radial distribution and study the radial dependence of scale-heights., Comment: Accepted by Astrophysics and Space Science, 11 pages, 4 figures

The coal bed stability classification is correct or not, which relates to directly the geological exploration type of coal resources and the correct assessment of the reasonable development and utilization value. Therefore, the study of the coal bed stability is very important. Based on the knowledge that the coal thickness change has the regional change and the partial change in the spatial distribution, and the disadvantages of the quantitative mathematical statistics methods, this article presented the new method of trend surface analysis and mathematical statistics combination, that is, the trend and variation method, to the quantitative evaluating coal bed stability, established the indicator system, including the minable index, the mean, the Coefficient of variation, the trend surface times, the trend surface fitting of the coal bed thickness, and the standard of the coal bed stability types. Took No.2 coal bed of Baie detailed exploration area in Shanxi as an application example, and it proved that the trend and variation method has obvious advantages on the coal bed stability evaluation, with making detailed contrasts and analysis of the results, which are evaluated respectively by the newly presented the trend and variation method and the traditional mathematical statistics method. The trend and variation method can reflect the discrete degree of the different coal bed thickness change and the spatial distribution and relativity of these coal thickness points value.