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The Dunhuang Mogao Grottoes are a significant cultural heritage site in the Silk Road, famous for its wonderful murals and statues. The rainfall causes the changes of humidity in the caves, which can easily activate the salts diseases of murals. In order to prevent the deterioration of the murals, the environmental monitoring tests were conducted to analyze the microclimate changes of the cave in rainfall weather, and proposed the risk prevention measures and suggestions. The results indicate that the temperature of caves has small change, but the humidity shows a clear trend of increase. The humidity and the duration of high humidity increases with the increase of the rainfall grade and frequency. The optimal starting time for environment control in the cave is when aatm and acave are consistent, and the relative humidity is controlled below 62%. The caves with lower layer, larger degree of openness and small volume are most vulnerable to water vapour diffusion. The environment monitoring should pay more attention to the continuous rainfall weather and the vulnerable caves. The research has great significance for the prevention of ancient mural deterioration. [ABSTRACT FROM AUTHOR]

Designated as a world heritage site by UNESCO in 1987, the Mogao Grottoes is famous for its cultural relics, in particular, the superb murals and painted sculptures. Moisture has been confirmed as the most active factor that could result in mural diseases. Therefore, ascertaining the moisture distribution of the cliff is of great significance for preventing the deterioration of murals and painted sculptures. In this study, a multi-electrode resistivity survey is applied atop the cliff of Mogao Grottoes. By deploying survey lines in two main study areas, the moisture distribution of the cliff is reflected by the resistivity profiles qualitatively. The results show that there is a mutually verifying relationship between the resistivity profiles and the water content of the exploratory well. In general, the resistivity of the cliff body is low in the distribution range of 1–300 Ω·m. It shows that the moisture content of these gullies atop the cliff is even lower. Besides, four potential danger areas are determined on the cliff face. Murals in these caves, which are excavated in these areas, will suffer more serious deterioration due to the moisture migration. The result also ascertains that the resistivity of the cliff could determine the moisture distribution inside the cliff. Moreover, this study can provide a firm scientific basis for protecting the valuable murals and painted sculptures in the caves. [ABSTRACT FROM AUTHOR]

The ramming technique is a traditional method used to improve the compactness of soil with impact and vibration energy. Based on the measured data of ramming force transmission and dissipation, this study reveals the mechanism of energy transfer and dissipation of single-layer ramming as well as the law of variation with ramming quality, laying thickness, and ramming times. It also establishes the ramming model and empirical formula of ramming quality, laying thickness, and ramming times, introduces the ramming layer changes associated with the constitutive relationship (elastic to elastoplastic parts) as a function of ramming times, and determines the influence depth and horizontal range based on real-time data monitoring. It was found that as the mass of the rammer increases, the range of influence of the impact stress inside the earth also increases proportionally, and this effect is more pronounced vertically. However, the dissipation rate of energy in horizontal direction is much greater than in the vertical direction. The traditional stacked ramming technique of "chong hai wo, hang yin ding" can effectively eliminate the defects of horizontal reversal upwelling impact and unevenness of the ramming layer during the ramming process. The research results provide a theoretical basis for evaluating the quality of the traditional ramming technique. [ABSTRACT FROM AUTHOR]

A series of double-limbs built-up I-section simply supported specimens subjected to compression were examined. The test columns contained 18 concentric compression columns and 12 eccentric compression columns with three section forms respectively. The influence of web stiffeners on buckling mode, ultimate bearing capacity and interaction between limbs were studied. It was shown that stiffeners in web effectively decreased the element width-to-thickness ratio and increased the bearing capacity of built-up I-section columns. But when larger eccentricity made the moment control the failure of eccentric compression specimens, the bearing capacity of the specimens was not improved obviously by web stiffeners. Distortional buckling could replace local buckling to control the failure modes of columns. Compared with double-limbs channel steel built-up open-sections with complex edge stiffeners under the same steel quantity and eccentricity, the load carrying capacity of double limb Σ-shaped channel built-up sections increased from 4.4% to 20.3%. While for double limb channel with V-type web stiffener sections, the increment was from 2.2% to 17.4%. Furthermore, parametric study of 90 Σ-shaped built-up section members was investigated to obtain the optimization proportion of the web sub-element and relationship of carrying capacity between single Σ-shaped section and double limb Σ-shaped I-section. Finally, the ultimate load-carrying capacity of built-up columns subjected to axial compression were calculated by two kinds of direct strength method formulas, which were compared with the tests values. The results showed that the method considered the interaction between distortional buckling and flexural buckling could obtain conservative results. [ABSTRACT FROM AUTHOR]

As urbanization and economic growth in developing countries expands, haze has become a global environmental problem in urban areas. Haze has obvious seasonal/daily variations across the globe. The concentration of fine particulate matter is higher in winter and lower in summer, and its daily variation shows bimodal characteristics. The objective of this paper is researching the formation mechanism of this pattern. The coupling between earth-air and fine particulate concentration is studied by monitoring and correlation analysis. Monitoring results have shown that earth-air pressure generally fluctuates with the overall atmospheric pressure. There is a mechanism of 'passive breathing' of earth-air, and due to the effect of seasonal/daily changes in soil temperature, 'autonomous breathing' also exists. The magnitude of the autonomous breathing effect is small (3.57 mm/d), whereas the passive breathing effect is much larger (421.25 mm/d). Correlation coefficients between volume of earth-air passive breathing and PM2.5 on yearly and daily timescales are 0.82 and 0.84, respectively. Statistical analysis suggests that when atmospheric pressure rises, atmospheric air is compressed, and concentration increases. At the same time, a part of the atmosphere enters the soil and causes back-mixing. When atmospheric pressure drops, atmospheric air expands, and filtered earth-air enters the atmosphere, reducing the near-surface PM2.5 concentration. This results in PM2.5 concentration changing synchronously with the earth-air passive breathing. Therefore, passive breathing of earth-air has important impact on the formation of haze patterns, and the atmospheric pumping effect provides the main driving force. [ABSTRACT FROM AUTHOR]

Based on the research results and practical engineering experience pertaining to the protection and reinforcement of the cliff of the Mogao Grottoes in Dunhuang, China, this paper presents a method that is mainly based on the analytic hierarchy process (AHP) to evaluate the preservation state and risk of the Mogao cliff, a means that numerical simulation was conducted to quantitatively evaluate the stability and effectiveness of protective measures for the Mogao cliff, a set of reinforcement methods which integrate the key protection techniques based on propping, anchoring, grouting, and anti-weathering and the quality control measures based on assessing their effectiveness for surrounding rocks of the grottoes, and a set of methods for monitoring and warning based on risk theory throughout the entire reinforcement process. The four above-mentioned techniques complement and support with each other, and every stage is based on research. Additionally, the protection and reinforcement concepts implemented at the Mogao cliff are summarized in this paper. Finally, preventive protection and reinforcement techniques for sandy conglomerate grottoes were established based on the research, evaluation, calculation, and monitoring. The techniques presented in this paper can be used as a theoretical foundation and provide technical guidance for the protection and reinforcement of similar cultural heritage sites all over the world. [ABSTRACT FROM AUTHOR]

Some of the largest and best-preserved Buddhist art treasure houses in the world, namely the Mogao Grottoes, are located at the northwest edge of the region of the Qinghai-Tibet plateau and are adjacent to the Altun and Qilian mountains, where the geotectonic activity is intense and large earthquakes have occurred. Future earthquakes are one of the major threats to the caves of the Mogao Grottoes; therefore, it is important that their dynamic performance is studied when an earthquake occurs. To understand the dynamic performance of the densely distributed caves under the effect of earthquakes, as well as the long-term stability of the Mogao Grottoes, the stress distribution, deformation characteristics, and peak-acceleration amplification factor were analysed under rare-earthquake conditions using a finite-difference element. The numerical study revealed that the most dangerous state of the caves is the initial time when an earthquake occurs. The obvious tensile stress concentration appeared at the top and the bottom of the caves of the middle floor; the main damage was caused by the shear failure towards the direction of the free face and not by the tensile failure. A large permanent horizontal displacement of the caves occurred after an earthquake, mostly at the densely distributed caves of the middle floor. The acceleration amplification effect of the middle-floor caves was significant; the Fourier amplitudes of the acceleration (which were monitored in all caves) were significantly magnified at the frequencies of 3 ~ 4 Hz and 7 ~ 9 Hz, whereas the Fourier amplitudes of the acceleration which were monitored in the middle-floor caves were almost amplified within the entire frequency range. Although the maximum stress was within the allowed limit and no tensile failure occurred, great permanent inhomogeneous horizontal displacements and large accelerations could have a negative effect on the stability of caves and the preservation of wall paintings. Moreover, it was assumed that the calculation results could serve as a type of guidance and as advice on the preventive protection of the Mogao Grottoes. [ABSTRACT FROM AUTHOR]

In this paper, a novel modified whale optimization algorithm based on Tent chaos map and tournament selection strategy (MWOA) was presented. The aim of the improved algorithm is to reduce the possibility of the standard whale algorithm falling into local optimal. During the initialization of the population, in order to increase population diversity and randomness, MWOA cites the Tent chaos map. In the optimization process, in order to improve the development ability of the standard algorithm, the tournament selection strategy was employed to improve the algorithm accuracy. Numerical simulation and example calculation results show that the improved algorithm is superior to the standard WOA algorithm. The improved method provides a new method for truss structure optimization. [ABSTRACT FROM AUTHOR]

Saline soil used in embankment construction causes dissolution falling and salt swelling, which results in embankment cracking. Therefore, saline soils should be stabilized in engineering. The unconfined compressive strength test, triaxial compressive test, splitting tensile test, and fatigue test were conducted on six types of stabilized soils. Subsequently, scanning electron microscopy test, X-ray diffraction test, Fourier transform infrared spectroscopy test, and thermogravimetric analysis were performed to discover the stabilizing mechanism. Test results indicated that the mechanical properties of saline soil were improved by adding lime, cement, fly ash, and SH agent (SH). In particular, after soaking, the strength of the stabilized soil with SH was significantly enhanced, the deviatoric stress-strain curves transformed from strain softening to strain hardening, and the tensile property and fatigue resistance were improved as well. The SH generated a film and silk-like web, wrapped the soil particles, and filled the soil pores, which improved the strength and anti-deformation abilities of the stabilized soils. [ABSTRACT FROM AUTHOR]

Keywords: Sandstone; Rock-hewn; Cave-temple; Deterioration patterns; Karsten tube; Sorptivity; Equotip hardness tester; Surface hardness EN Sandstone Rock-hewn Cave-temple Deterioration patterns Karsten tube Sorptivity Equotip hardness tester Surface hardness 2915 2920 6 06/05/20 20200601 NES 200601 Introduction Rock-hewn cave-temples are a form of Buddhist temple architecture. Second, the hardness of each sandstone bed (up to 1.5 m above the ground) at four sites (three niches and the natural rock face to the north of the NGT façade) was measured using a Proceq Equotip 3 hardness tester (with D probe) (see Figs. In addition, it is worth noting that where alveolar weathering is found, surface hardness values are slightly greater than the average surface hardness of all beds at that measurement location, such as layer d at niche 101. Sandstone, Rock-hewn, Cave-temple, Deterioration patterns, Karsten tube, Sorptivity, Equotip hardness tester, Surface hardness. [Extracted from the article]

The Mogao Grottoes is famous around the world for its exquisite wall paintings and colorful painted sculptures, and was inscribed in the UNESCO World Heritage List in 1987. Although the site is located in an arid area, water is still one of the main factors threatening the long-term preservation of cultural relics. The relationship between rainfall infiltration and wall painting deterioration was investigated as part of efforts to develop conservation strategies to prevent deterioration caused by atmospheric precipitation. This was done through artificial rainfall simulation experiments and high-density electrical non-destructive test. Areas prone to wall painting deterioration, as evidenced by periodic condition assessment, showed an association between further deterioration and natural heavy rainfall. The results show that the covering layer above the grottoes has a small runoff coefficient, and the rainfall infiltration is much larger than the volume of runoff produced. The rainwater migrates preferentially along the rock fractures in the form of gas or through the gaps between the grotto eaves and the rock, or through cracks in the form of liquid. This is the main mechanism for activation of salt damage and deterioration of the wall paintings. The covering layer above the grottoes is thin, and the through-cracks in the surrounding rock or external wooden eaves are particularly vulnerable to rainfall infiltration. This indicates that more attention should be paid to the system of preventive protection by rainwater disposal. This research has important practical value in improving preventive protection of the Mogao Grottoes. [ABSTRACT FROM AUTHOR]

The Dunhuang Mogao Grotto is a famous Buddhist monument and was inscribed in the list of world cultural heritage sites by UNESCO in 1987. Water poses a major threat to the preservation of this heritage even though it is located in an arid region. This study was conducted to investigate the effect of rainfall on rock erosion. Specifically, the formation mechanism of slope runoff and the erosion threshold of rainfall were analyzed, and erosion-prone areas of the site were identified. This was carried out using field artificial rainfall simulation testing, and the results inform methods of preventing rainfall-induced cliff erosion. In addition, the rainfall threshold and erosion-prone areas obtained from the experiment were further validated and optimized using monitoring data for natural rainfall and historic documentation. The threshold value of erosive rainfall obtained by empirical statistical analysis method was found to be similar to that obtained by the runoff generation mechanism. The areas identified as prone to erosion using field tests coincided with areas of historic erosion as recorded in site documentation. Furthermore, the forecast grade of cliff slope erosion and its erosion-prone areas are determined after comprehensive analysis of the results obtained by these two methods. The research results are critical for the monitoring, early warning, and prevention of cliff slope erosion. The research methods can also be used as reference in areas for which rainfall data are missing. [ABSTRACT FROM AUTHOR]

The Mogao Grottoes are among the most famous sites on the World Heritage list. Several large-scale preservation projects were implemented in 1962, 1982, and 2008, respectively, to improve their preservation conditions. According to field investigation and assessment in recent years, the cliff is stable on the whole because of the reinforcement projects. Among them, there are still 42 potentially dangerous bodies, which may not be stable in some conditions. For the purpose of building the monitoring and early warning system and the long-term preventive preservation of the Mogao Grottoes, an innovative analytical method based on the Analytic Hierarchy Process (AHP) and Fuzzy-AHP was applied to assess the hazard of potentially dangerous bodies within the cliff. Firstly, the hazard was classified into six groups: very high, high, moderate, low, very low, and no hazard, in this study. Secondly, the AHP method was applied to calculate the impact index of each causative factor, and then the hazard assessment of dangerous bodies was made based on statistical analysis. Finally, the Fuzzy-AHP method was applied to calculate the correlation of each factor and determine the comprehensive hazard class. The results indicate that Fuzzy-AHP seems to be more accurate than AHP in hazard assessment. Meanwhile, there is a very high risk body that can threaten 10 caves, three high risk bodies that can threaten 13 caves, and 15 moderate risk bodies can threaten 69 caves in total, while the remaining bodies are defined as low or very low grades. Overall, the results of this study provide much data and a theoretical model in the construction of a monitoring and early warning system currently. Furthermore, the new numerical simulation method also holds the potential application to assess the hazards of other types of heritage sites. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) is investigated as a function of the excitation intensity and temperature for lattice-matched InGaAs/InAlAs quantum well (QW) structures with well thicknesses of 7 and 15 nm, respectively. At low temperature, interface fluctuations result in the 7-nm QW PL exhibiting a blueshift of 15 meV, a narrowing of the linewidth (full width at half maximum, FWHM) from 20.3 to 10 meV, and a clear transition of the spectral profile with the laser excitation intensity increasing four orders in magnitude. The 7-nm QW PL also has a larger blueshift and FWHM variation than the 15-nm QW as the temperature increases from 10 to ~50 K. Finally, simulations of this system which correlate with the experimental observations indicate that a thin QW must be more affected by interface fluctuations and their resulting potential fluctuations than a thick QW. This work provides useful information on guiding the growth to achieve optimized InGaAs/InAlAs QWs for applications with different QW thicknesses. [ABSTRACT FROM AUTHOR]

An experimental investigation of the carbon concentration effects on the emission intensity has been carried out using laser-induced plasma spectroscopy. The results show that the intensity of Ca II 393.367 nm and 396.847 nm characteristic lines emitted in the sample with the carbon concentration of 25% is about five times larger than that in the pure soil sample. It can be attributed to the high heat transfer coefficient and low ionization potentials of carbon in the system. Using the best experimental condition, quantitative analysis of the trace element of lead is conducted and the detection limit of lead concentration is estimated to be below 0.02%. [ABSTRACT FROM AUTHOR]

The Sr3SiO5:Eu2+ phosphor was synthesized by high temperature solid-state reaction. The emission spectrum of Sr3SiO5:Eu2+ shows two bands centered at 487 and 575 nm, which well agree with the theoretic values of emission spectrum. The excitation spectrum for 575 nm emission center has several excitation bands at 365, 418, 458 and 473 nm. And the results show that the emission spectrum of Sr3SiO5:Eu2+ is influenced by the Eu2+ concentration. The relative emission spectra of the white-emitting lnGaN-based YAG:Ce3+ LED and Sr3SiO5:Eu2+ LED were investigated. The results show that the color development of InGaN-based Sr3SiO5:Eu2+ is better than that of lnGaN-based YAG:Ce3+, and the CIE chromaticity of lnGaN-based Sr3SiO5:Eu2+ is (x=0.348, y=0.326). [ABSTRACT FROM AUTHOR]

Mogao Grottos are located at the eastern foot of the Mingsha Mountain, 25 km southeast of Dunhuang City. The caves were excavated into the cliff on the west bank of the Daquan River. The wall paintings in the caves are subject to the severe deterioration generated by recrystallization of salt. It relates with the movement of water/moisture in rock formation. Through the satellite image analysis and geological survey, it has been clarified that the movement of ground water is governed by the fault system. The geographical nature is specified by the aggressive tectonic movement from the south. [ABSTRACT FROM AUTHOR]

Uncertainties over future climatic conditions pose significant challenges when selecting appropriate conservation strategies for heritage sites. Choosing effective strategies is especially important for earthen heritage sites located in dryland regions, as many are experiencing rapid environmentally-driven deterioration. We use a newly developed cellular automaton model (ViSTA-HD), to evaluate the environmental deterioration risk, over a 100-year period, under a range of potential climate and conservation scenarios. Results show increased wind velocities could substantially increase the overall deterioration risk, implying the need for wind-reducing conservation strategies. In contrast, predicted increases in rainfall are not likely to increase the overall deterioration risk, despite greater risk of rain-driven deterioration features. Of the four conservation strategies tested in our model, deterioration risk under all climatic scenarios was best reduced by increasing the coverage of natural, randomly-distributed vegetation to 80%. We suggest this approach could be an appropriate long-term conservation strategy for other earthen sites in dryland regions. [ABSTRACT FROM AUTHOR]