Search

CO2-hardened sand with water glass binders are commonly used in the manufacturing of molds and cores, but the adsorption mechanism of CO2molecules on the surface of sodium and potassium silicate under different pressures is still unclear. This work investigates the absorption properties of CO2molecules both at the (100) surface of sodium silicate and the (100) surface of potassium silicate by Materials Studio software. It turns out that the pressure is crucial in absorption behavior, the relationship between the adsorption of CO2and pressure is nonlinear. The absorption tendency of CO2at (100) surface of sodium silicate is higher than that of potassium silicate. CO2tends to be absorbed by sodium silicate when modeling the CO2adsorption between the (100) surface layers of potassium silicate and sodium silicate. These adsorption properties are beneficial to provide theoretical support for the optimization of the process of CO2-hardened sand with water glass binders.

This paper has developed a new compound curing agent powder for a modified phosphate binder (3 wt% of raw sand). This combination can be self-cured and achieve relatively high bonding strength. The optimal composition ratio of curing agent powder is fused magnesia powder:silica fume:sodium polyacrylate at a ratio of 6:6:5, respectively. In this case, the tensile strength of phosphate binder sand sample at 4 h and 24 h is 0.65 MPa and 1.27 MPa, respectively. Infrared spectroscopy and scanning electron microscopy were utilized to analyze the variation of functional groups and the morphology of bonding bridge fracture of phosphate bonded sand samples after the addition of curing agent (fused magnesia powder, silica fume and sodium polyacrylate). The result shows that fused magnesia powder, silica fume and sodium polyacrylate all participate in the polymerization and curing reaction of phosphate binder; furthermore, sodium polyacrylate can effectively mitigate the propagation of cracks on bonding film.

This case study of the Hexi Corridor, Northwestern China, utilizes statistical methods to estimate quantitatively the interaction at a regional level between climate change, ancient social developments, and political coping strategies over the past 2000 years. The data is sourced from high-resolution reconstructions of climate series (temperature and precipitation), and historical records of cultivated land, war, population, and changes in regional administrative systems. The results show that moisture conditions played a more significant role than temperature in driving land reclamation in the Hexi Corridor. Analysis also showed a negative correlation between war frequency and the area of cultivated land in the Corridor over 20-year time intervals. Population growth was found to have a significant positive correlation with the cultivated land area during the study period. The results indicate that a climate-induced decline in agricultural production and the subsequent fluctuations in population could act as a trigger for social unrest, which is especially true at the mutual decadal time-scales. However, the interaction with administrative reform also suggests that, in the face of social and economic turmoil, a reasonable administrative hierarchy could strengthen the social governance of regional government, and promote social stability and economic development at a regional level. The study substantiates this notion with empirical quantitative evidence.

This paper presents new high-resolution proxies and paleoclimatic reconstructions for studying climate changes in China for the past 2000 years. Multi-proxy synthesized reconstructions show that temperature variation in China has exhibited significant 50–70-yr, 100–120-yr, and 200–250-yr cycles. Results also show that the amplitudes of decadal and centennial temperature variation were 1.3°C and 0.7°C, respectively, with the latter significantly correlated with long-term changes in solar radiation, especially cold periods, which correspond approximately to sunspot minima. The most rapid warming in China occurred over AD 1870–2000, at a rate of 0.56° ± 0.42°C (100 yr)−1; however, temperatures recorded in the 20th century may not be unprecedented for the last 2000 years, as data show records for the periods AD 981–1100 and AD 1201–70 are comparable to the present. The ensemble means of dryness/wetness spatial patterns in eastern China across all centennial warm periods illustrate a tripole pattern: dry south of 25°N, wet from 25°–30°N, and dry to the north of 30°N. However, for all centennial cold periods, this spatial pattern also exhibits a meridional distribution. The increase in precipitation over the monsoonal regions of China associated with the 20th century warming can primarily be attributed to a mega El Ni˜no–Southern Oscillation and the Atlantic Multidecadal Oscillation. In addition, a significant association between increasing numbers of locusts and dry/cold conditions is found in eastern China. Plague intensity also generally increases in concert with wetness in northern China, while more precipitation is likely to have a negative effect in southern China. 本文综述了近来中国过去2000年气候变化研究中新取得的高分辨率代用资料和重建序列。结果显示: (1) 中国温度存在50–70年、100–120年和200–250年的准周期变化, 其年代和百年际变幅分别约为1.3℃和0.7℃, 且在百年尺度上与太阳辐射的长期变化显著相关, 尤其是气温寒冷阶段与太阳活动极小期相对应。 (2) 1870–2000年是中国增温最快的阶段, 速率为0.56 ± 0.42°C (100 yr)−1, 但20世纪的气温记录可能并不是过去2000年未曾出现过的, 重建表明公元981–1100年和1201–1270年间的温暖程度可与之相比。 (3) 对中国东部所有百年尺度暖期的集合平均显示其旱涝格局呈三极空间分布: 25°N以南偏旱, 25°–30°N偏涝, 30°N以北偏旱; 而在所有百年尺度冷期旱涝格局则呈经向分布。 (4) 强厄尔尼诺–南方涛动和北大西洋年代际振荡是导致20世纪中国季风区降水增加的主要原因。 (5) 在中国东部, 蝗灾与温度及降水变化显著相关, 干冷气候条件下蝗灾较多; 北部地区的鼠疫与干湿变化呈正相关, 但南方地区的鼠疫却与干湿变化呈负相关。

Yougui pill (YGP) is a well-known Chinese medicine formula with definite clinical effects on kidney-yang deficiencies such as infertility. However, Aconitum carmichaelivar. carmichaeli, one of the herbs contained in YGP, shows several side effects. Therefore, it is important to carry out strict and systematic quality evaluation on YGP to ensure its effects and safety. In the present study, qualitative and quantitative analyses were performed on YGP. First, an HPLC-LTQ-Orbitrap-MSnmethod was applied to validate the chemical profile of YGP. Eighty-three compounds were identified, including iridoids, flavones and alkaloids. Second, an UPLC-QqQ-MS/MS method was used for the simultaneous quantitation of 16 targeted compounds in YGP. The method showed a good linear correlation (R> 0.995) over a wide range and a high sensitivity, as established by LOD (0.04–0.40 ng mL−1) and LOQ (0.10–1.00 ng mL−1). The RSD values of intra- and inter-day precisions were less than 10%. The RSD values of repeatability and stability were less than 5%, and recovery assays were between 85.8% and 96.2%. The cluster analysis indicated that the qualities of YGP from two manufacturers were very different. The present integrated qualitative and quantitative assessment of YGP provides a good example of quality evaluation strategy to assess Chinese medicine formulas.

Phenological data obtained from historical documents constitute highly important ecological evidence for the pre-instrumental period, and can be used in analyzing climatic change in history. In this study, 87 phenological records about seasonality of non-biological events (e.g., first frost date), agriculture and ornamental plants (e.g., first flowering date) over 77 years were extracted from historical documents from the Sui and Tang dynasties in China to reconstruct the winter half-year (from October to next April) temperatures in the Guanzhong Area (located in central China) from 600 to 902 AD. Transfer functions between temperature and phenophases with significant correlations were established by using modern observation data. Temperatures from the study period were reconstructed by applying the transfer functions to historical phenological data. The reconstruction indicates that the winter half-year temperatures during 600–902 AD were 0.23°C higher than the reference period (1961–1990). The temperature changed with two distinct stages. During the 600s–800s, temperatures were approximately 0.38°C higher than at present but then temperatures decreased in the subsequent period (800–902 AD). These results are similar to ones from previous studies on the mean temperature and the divisions between warm and cold periods during the study period, though differences were found in the degree of warmness/coldness. This reconstruction provides a valuable contribution to a better understanding of climatic variability during the Sui and Tang dynasties in China.

The general characteristics of climate changes over the past 2000 years in China, regional differences and uncertainties were analyzed based on the recently peer-reviewed high time-resolution climatic reconstructions. The results showed that there exists four warm periods of the temperature variation in China since the Qin Dynasty, including the western and eastern Han Dynasties (200 BC-AD 180), the Sui and Tang dynasties (541–810), the Song and Yuan dynasties (931–1320), and the 20th century, and three cold phases involving the Wei, Jin, and North-South Dynasties (181–540), the late Tang Dynasty (811–930), and the Ming and Qing dynasties (1321–1920). The Song and Yuan warm period is consistent with the Medieval Warm Period over the Northern Hemisphere, and the cold phases of the North-South Dynasties and the Ming and Qing dynasties are paralleled to the Dark Ages Cold Period and the Little Ice Age, respectively. The 13th-15th century could be a shift to the wet condition of the climate, and the low precipitation variability is exhibited in western China prior to 1500. In the context of the climate warming, the pattern of the drought in north and flood in south is prevalent over the eastern China. In addition, the published reconstructions have a high level of confidence for the past 500 years, but large uncertainties exist prior to the 16th century.The general characteristics of climate changes over the past 2000 years in China, regional differences and uncertainties were analyzed based on the recently peer-reviewed high time-resolution climatic reconstructions. The results showed that there exists four warm periods of the temperature variation in China since the Qin Dynasty, including the western and eastern Han Dynasties (200 BC-AD 180), the Sui and Tang dynasties (541–810), the Song and Yuan dynasties (931–1320), and the 20th century, and three cold phases involving the Wei, Jin, and North-South Dynasties (181–540), the late Tang Dynasty (811–930), and the Ming and Qing dynasties (1321–1920). The Song and Yuan warm period is consistent with the Medieval Warm Period over the Northern Hemisphere, and the cold phases of the North-South Dynasties and the Ming and Qing dynasties are paralleled to the Dark Ages Cold Period and the Little Ice Age, respectively. The 13th-15th century could be a shift to the wet condition of the climate, and the low precipitation variability is exhibited in western China prior to 1500. In the context of the climate warming, the pattern of the drought in north and flood in south is prevalent over the eastern China. In addition, the published reconstructions have a high level of confidence for the past 500 years, but large uncertainties exist prior to the 16th century.