Effects of the initiation position on the damage and fracture characteristics of linear-charge blasting in rock

To study the effects of the initiation position on the damage and fracture characteristics of linear-charge blasting, blasting model experiments were conducted in this study using computed tomography scanning and three-dimensional reconstruction methods. The fractal damage theory was used to quantify the crack distribution and damage degree of sandstone specimens after blasting. The results showed that regardless of an inverse or top initiation, due to compression deformation and sliding frictional resistance, the plugging medium of the borehole is effective. The energy of the explosive gas near the top of the borehole is consumed. This affects the effective crushing of rocks near the top of the borehole, where the extent of damage to Sections Ⅰ and Ⅱ is less than that of Sections Ⅲ and Ⅳ. In addition, the analysis revealed that under conditions of top initiation, the reflected tensile damage of the rock at the free face of the top of the borehole and the compression deformation of the plug and friction consume more blasting energy, resulting in lower blasting energy efficiency for top initiation. As a result, the overall damage degree of the specimens in the top-initiation group was significantly smaller than that in the inverse-initiation group. Under conditions of inverse initiation, the blasting energy efficiency is greater, causing the specimen to experience greater damage. Therefore, in the engineering practice of rock tunnel cut blasting, to utilize blasting energy effectively and enhance the effects of rock fragmentation, using the inverse-initiation method is recommended. In addition, in three-dimensional(3D) rock blasting, the bottom of the borehole has obvious end effects under the conditions of inverse initiation, and the crack distribution at the bottom of the borehole is trumpet-shaped. The occurrence of an end effect in the 3D linear-charge blasting model experiment is related to the initiation position and the blocking condition.

A hybrid CNN-LSTM model for diagnosing rice nutrient levels at the rice panicle initiation stage

Nitrogen(N)and potassium(K)are two key mineral nutrient elements involved in rice growth.Accurate diagnosis of N and K status is very important for the rational application of fertilizers at a specific rice growth stage.Therefore,we propose a hybrid model for diagnosing rice nutrient levels at the early panicle initiation stage(EPIS),which combines a convolutional neural network(CNN)with an attention mechanism and a long short-term memory network(LSTM).The model was validated on a large set of sequential images collected by an unmanned aerial vehicle(UAV)from rice canopies at different growth stages during a two-year experiment.Compared with VGG16,AlexNet,GoogleNet,DenseNet,and inceptionV3,ResNet101 combined with LSTM obtained the highest average accuracy of 83.81%on the dataset of Huanghuazhan(HHZ,an indica cultivar).When tested on the datasets of HHZ and Xiushui 134(XS134,a japonica rice variety)in 2021,the ResNet101-LSTM model enhanced with the squeeze-and-excitation(SE)block achieved the highest accuracies of 85.38 and 88.38%,respectively.Through the cross-dataset method,the average accuracies on the HHZ and XS134 datasets tested in 2022 were 81.25 and 82.50%,respectively,showing a good generalization.Our proposed model works with the dynamic information of different rice growth stages and can efficiently diagnose different rice nutrient status levels at EPIS,which are helpful for making practical decisions regarding rational fertilization treatments at the panicle initiation stage.

Molecular cloning,characterization and promoter analysis of LbgCWIN1 and its expression profiles in response to exogenous sucrose during in vitro bulblet initiation in lily

Lily(Lilium spp.) is an important ornamental flower, which is mainly propagated by bulbs. Cell wall invertases(CWINs), which catalyze the irreversibly conversion of sucrose into glucose and fructose in the extracellular space, are key enzymes participating in sucrose allocation in higher plants. Previous studies have shown that CWINs play an essential role in bulblet initiation process in bulbous crops, but the underlying molecular mechanism remains unclear. Here, a CWIN gene of Lilium brownii var. giganteum(Lbg) was identified and amplified from genomic DNA. Quantitative RT-PCR assays revealed that the expression level of LbgCWIN1 was highly upregulated exactly when the endogenous starch degraded in non-sucrose medium during in vitro bulblet initiation in Lbg. Phylogenetic relationship, motif, and domain analysis of LbgCWIN1 protein and CWINs in other plant species showed that all sequences of these CWIN proteins were highly conserved. The promoter sequence of LbgCWIN1 possessed a number of alpha-amylase-, phytohormone-, light-and stress-responsive cis-elements. Meanwhile, β-glucuronidase(GUS) assay showed that the 459 bp upstream fragment from the translational start site displayed maximal promoter activity. These results revealed that LbgCWIN1 might function in the process of in vitro bulblet initiation and be in the response to degradation of endogenous starch.

Shock Initiation Experiments with Modeling on a DNAN Based MeltCast Insensitive Explosive

2,4-dinitroanisole(DNAN)is a good replacement for 2,4,6-trinitrotoluene(TNT)in melt-cast explosives due to its superior insensitivity.With the increasing use of DNAN-based melt-cast explosives,the prediction of reaction violence and hazard assessment of the explosives subjected to shock is of great significance.This study investigated the shock initiation characteristics for a DNAN-based melt-cast explosive,DHFA,using the one-dimensional Lagrangian apparatus.The embedded manganin gauges in the apparatus record the pressure histories at four Lagrangian positions and show that shock-todetonation transition in DHFA needs a high input shock pressure.The experimental data are analyzed to calibrate the Ignition and Growth model.The calibration is performed using an objective function based on both pressure history and the arrival time of shock.Good agreement between experimental and calculated pressure histories indicates the high accuracy of the calibrated parameters with the optimization method.

Actors of Psychoactive Drug Initiation among Adolescents in Yaoundé-Cameroon

Introduction: Actors of psychoactive drug initiation refer to those who introduce others to psychoactive drug use (initiators) and those who are introduced to psychoactive drugs (users). By identifying their features, better prevention and intervention programs can be developed to reduce psychoactive drug use among adolescents. This article describes the role of actors of psychoactive drug initiation among teenagers in secondary schools in Yaoundé (Cameroon). Methodology: A cross sectional study was carried out in twelve secondary schools in Yaoundé from October 2022 to May 2023. Adolescents from Form four to upper sixth, who assented to participate in the study and received parental consent were included. Data were collected in a structured self-reported questionnaire and analyzed using SPSS 23. Quantitative variables were expressed using means, standard deviations, median and interquartile ranges depending on the distribution of data. Qualitative variables were expressed in the form of frequency and percentages. Results: Drug use was more prevalent among male adolescents (55.3%) from nuclear families (91.4%) who received relatively high pocket money. The main sources of drug exposure were non-family members (49.7%), especially friends outside school. The most frequent place of initiation was snack bars (33.1%). Conclusion: The study revealed the importance of the family, friends and leisure places in the initiation process of drug use in teenagers. Based on these results, parents and school authorities should work together to create a safe and supportive environment that fosters communication, education to prevent drug abuse among adolescents in Yaoundé.

Brassinosteroids Mediate Endogenous Phytohormone Metabolism to Alleviate High Temperature Injury at Panicle Initiation Stage in Rice

High temperatures cause physiological and biochemical changes and significantly affect young panicle development of rice(Oryza sativa L.).Brassinosteroids play important roles in enhancing crop stress resistance.In this study,we subjected rice cultivars Huanghuazhan(heat-resistant)and IR36(heat-sensitive)to high temperature(HT,40 oC)or normal temperature(NT,33 oC)for 7 d at the panicle initiation stage,in conjunction with application of 24-epibrassinolide[EBR,a synthetic brassinolide(BR)]or brassinazole(BRZ,a BR biosynthesis inhibitor)at the beginning of the treatments.HT exacerbated spikelet degeneration and inhibited young panicle growth,which were partially prevented by EBR application,while BRZ application aggravated the reduction in spikelet number.HT decreased the contents of BR,active cytokinins(aCTK),active gibberellins(aGA)and indole-3-acetic acid(IAA),but increased the content of abscisic acid(ABA)in young panicles.The activities of key enzymes involved in sucrose hydrolysis,glycolysis and the tricarboxylic acid cycle in young panicles were decreased with the change of endogenous hormone levels under HT.In addition,the contents of H2O2 and malondialdehyde(MDA)were increased and the activities of antioxidant enzymes were decreased in young panicles.Exogenous application of EBR induced the expression of phytohormone biosynthesis-related genes and down-regulated the expression of phytohormone catabolism-related genes to increase the contents of endogenous BR,aCTK,aGA and ABA,thus promoting the decomposition and utilization of sucrose in young panicles,enhancing the activities of superoxide dismutase,catalase and peroxidase,and reducing the accumulation of H2O2 and MDA in young panicles,whereas application of BRZ had the opposite physiological effects.These results showed that brassinosteroids mediate endogenous phytohormone metabolism to alleviate HT injury at the panicle initiation stage in rice.

Impact of orientation of blast initiation on ground vibrations

The blast-induced ground vibrations can be significantly controlled by varying the location and orien-tation of point of interest from blast site.The blast waves generated due to individual holes get super-imposed and resultant peak particle velocity(PPV)generates.With the orientation sequence of holes blasts on site,the superimposition angle of wave changes and hence results in significant variation in resultant PPV.The orientation with respect to the initiation of blasts resulting in lowest PPV needs to be identified for any site.By knowing the PPV contour of vibration waves in mine sites,it is possible to reduce the vibration on the structures by changing the initiation sequence.In this paper,experimental blasts were conducted at two different mine sites and the PPV values were recorded at different ori-entations from the blast site and its initiation sequence.The PPV contours were drawn to identify the orientation with least and highest PPV generation line.It was found that by merely changing the initi-ation sequence of blasts with respect to the sensitive structure or point of interest,the PPV values can be reduced significantly up to 76.9%.

Discussion on “Impact of orientation of blast initiation on ground vibrations” [J Rock Mech Geotech Eng 15 (2022) 255e261]

Recently,Garai et al.(2022)published a paper on the impact of orientation of blast initiation on ground vibrations.However,some of the claims are not supported by the results of the given tests.In Fig.1(see Fig.8 in Garai et al.,2022),there are contours of measured vibration velocities in 4 directions(every 90?)and an incorrect interpretation between them.By placing all measured vibration velocity values(Gerai et al.,2022)at well-defined points on a single figure,it was not possible to precisely determine the type of vibration velocity,such as radial,tangential and vertical vibration velocities,with their different shapes.An incorrect conclusion was also drawn about the direction of the highest vibration velocity.The paper by Garai et al.(2022)measured the vibrational velocity of the medium through which the seismic wave passed,but used the incorrect term shock wave.The shock wave would have destroyed the seismic measuring instruments.A superposition of the vibrational velocity was considered,but not combined with the vibrational frequency of the seismic wave.This paper presents a method for selecting the time delay between successively initiated explosive charges to the measured frequency of the seismic wave,so that the direction of initiation of the explosive charges does not affect the vibration velocity of the ground through which the seismic wave passes.The theoretical and measured shapes and waveforms of radial velocity and tangential velocity in an opencast lignite mine are then presented.Moreover,the conditions for the formation of shock wave,transition wave and seismic waves are presented.

Translocation and Distribution of Carbon-Nitrogen in Relation to Rice Yield and Grain Quality as Affected by High Temperature at Early Panicle Initiation Stage

Due to climate change, extreme heat stress events have become more frequent, adversely affecting rice yield and grain quality. The accumulation and translocation of dry matter and nitrogen substances are essential for rice yield and grain quality. To assess the impact of high temperature stress(HTS) at the early panicle initiation(EPI) stage on the accumulation, transportation, and distribution of dry matter and nitrogen substances in various organs of rice, as well as the resulting effects on rice yield and grain quality, pot experiments were conducted using an indica rice cultivar Yangdao 6(YD6) and a japonica rice cultivar Jinxiangyu 1(JXY1) under both normal temperature(32 ℃/26 ℃) and high temperature(38 ℃/29 ℃) conditions. The results indicated that exposure to HTS at the EPI stage significantly decreased rice yield by reducing spikelet number per panicle, grain-filling rate, and grain weight. However, it improved the nutritional quality of rice grains by increasing protein and amylose contents. The reduction in nitrogen and dry matter accumulation accounted for the changes in spikelet number per panicle, grain-filling rate, and grain size. Under HTS, the decrease in nitrogen accumulation accompanied by the reduction in dry matter may be due to the down-regulation of leaf net photosynthesis and senescence, as evidenced by the decrease in nitrogen content. Furthermore, the decrease in sink size limited the translocation of dry matter and nitrogen substances to grains, which was closely related to the reduction in grain weight and the deterioration of grain quality. These findings significantly contribute to our understanding of the mechanisms of HTS on grain yield and quality formation from the perspective of dry matter and nitrogen accumulation and translocation. Further efforts are needed to improve the adaptability of rice varieties to climate change in the near future.

Detonation driving rules for cylindrical casings under asymmetrical multipoint initiations

The detonation wave-aiming warhead can effectively enhance the lethality efficiency. In the past, rules for casing rupture and velocity distribution under asymmetrical initiations were not adequately investigated. In this study, X-ray photography and numerical modelling are used to examine the casing expansions under centre point, asymmetrical one-point, and asymmetrical two-point(with central angles of 45° and 90°) initiations. The results indicate that early casing ruptures are caused by local high pressures, induced by the initiation, detonation wave interaction, and Mach wave onset. The fragment shapes are controlled by the impact angle of the detonation wave. The fragment velocity distributions differ under different initiation types, and the end rarefaction waves can affect the velocity distribution.This study can serve as a reference for the design and optimization of high-efficiency warheads.

A new Ignition-Growth reaction rate model for shock initiation

Accurately predicting reactive flow is a challenge when characterizing an explosive under external shock stimuli as the shock initiation time is on the order of a microsecond.The present study constructs a new Ignition-Growth reaction rate model,which can describe the shock initiation processes of explosives with different initial densities,particle sizes and loading pressures by only one set of model parameters.Compared with the Lee-Tarver reaction rate model,the new Ignition-Growth reaction rate model describes better the shock initiation process of explosives and requires fewer model parameters.Moreover,the shock initiation of a 2,4-Dinitroanisole(DNAN)-based melt-cast explosive RDA-2(DNAN/HMX(octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazoncine)/aluminum)are investigated both experimentally and numerically.A series of shock initiation experiments is performed with manganin piezoresistive pressure gauges and corresponding numerical simulations are carried out with the new Ignition-Growth reaction rate model.The RDA-2 explosive is found to have higher critical initiation pressure and lower shock sensitivity than traditional explosives(such as the Comp.B explosive).The calibrated reaction rate model parameters of RDA-2 could provide numerical basis for its further application.

Characterization of subduction initiation

Compression is required for all kinds of subduction initiations,which may cause either subsidence or uplift,depending on the ages of the oceanic plates.Subduction initiations associated with the old oceanic crust tend to amplify preexisting subsidence by compression,whereas those associated with young oceanic plates may result in uplift.

Gaps,challenges and possible solution for prediction of wheel-rail rolling contact fatigue crack initiation

The prediction of wheel/rail rolling contact fatigue(RCF)crack initiation during railway operations is an important task.Since RCF crack evolution is influenced by many factors,its prediction process is complex.This paper reviews the existing approaches to predict RCF crack initiation.The crack initiation region is predicted by the shakedown map.By combining the shakedown map with various initiation criteria and the critical plane method,the crack initiation life is calculated.The classification,methodologies,theories and applications of these approaches are included in this paper.The advantages and limitations of these methods are analyzed to provide recommendation for RCF crack initiation prediction.This review highlights that wheel/rail dynamic characteristic,complex working conditions,surface defects and wear all affect the RCF crack initiation.The optimal selection of criteria is essential in the crack initiation prediction.Based on the research gap regarding the challenging process of crack initiation prediction detailed in this review,a proposed prediction process of RCF crack initiation is proposed to achieve a more accurate result.

Coupling between the Cenozoic west Pacific subduction initiation and decreases of atmospheric carbon dioxides

At the beginning of the Cenozoic,the atmospheric CO_(2)concentration increased rapidly from~2000 ppmv at 60 Ma to~4600 ppmv at 51 Ma,which is 5–10 times higher than the present value,and then continuous declined from~51 to 34 Ma.The cause of this phenomenon is still not well understood.In this study,we demonstrate that the initiation of Cenozoic west Pacific plate subduction,triggered by the hard collision in the Tibetan Plateau,occurred at approximately 51 Ma,coinciding with the tipping point.The water depths of the Pacific subduction zones are mostly below the carbonate compensation depths,while those of the Neo-Tethys were much shallower before the collision and caused far more carbonate subducting.Additionally,more volcanic ashes erupted from the west Pacific subduction zones,which consume CO_(2).The average annual west Pacific volvano eruption is 1.11 km~3,which is higher than previous estimations.The amount of annual CO_(2)absorbed by chemical weathering of additional west Pacific volcanic ashes could be comparable to the silicate weathering by the global river.We propose that the initiation of the western Pacific subduction controlled the long-term reduction of atmospheric CO_(2)concentration.

“三大倡议”与新时期中国的中亚外交

自2021年以来,习近平主席相继提出了全球发展倡议、全球安全倡议和全球文明倡议三大全球性倡议。“三大倡议”不仅为解决全球性问题提供了重要方案,而且为中国的中亚外交提供了理论支持和战略引领。中国同中亚五国是命运与共的好邻居、好朋友、好伙伴、好兄弟。三十多年来,中国的中亚外交取得了令人瞩目的巨大成就。当前,中国应以全球发展倡议为引领,推动中国与中亚国家实现共同发展;以全球安全倡议为引领,助力中国与中亚国家实现共同安全;以全球文明倡议为引领,促进中国与中亚国家实现民心相通与文明互鉴,进而促进中国与中亚国家走上更加稳定和友好的发展轨道,并保障中国—中亚命运共同体的构建取得更多切实成效。

马克思、恩格斯关于历史主动精神的论述和现实启示

历史主动精神植根于唯物史观,是指无产阶级在遵循历史规律的前提下主动创造历史的精神品质。这种精神在重大历史关头表现得更为鲜明,其本质是人的主观能动性的发挥。马克思、恩格斯关于历史主动的论述使用了“历史主动性”“主动精神”“历史首创精神”等核心概念。围绕这些核心概念,马克思、恩格斯以人民群众、无产阶级和无产阶级政党为主体展开了关于历史主动精神的论述。其内涵主要包括主动斗争精神、主动创造精神和主动引领精神。马克思、恩格斯关于历史主动精神的论述为马克思主义的发展与传播奠定了基础,也推动了共产主义运动和中国革命的发展。探究马克思、恩格斯关于历史主动精神的论述有助于在新征程中彰显中国共产党人的马克思主义立场,激发更为主动的精神力量。

希夏邦马峰地区始新世地壳加厚和隆升过程

中新世中期之前喜马拉雅山脉的隆升历史和深部动力机制,还存在极大的争议、缺乏基本的数据约束。喜马拉雅造山带核部高级变质岩的埋藏和折返过程可以约束地壳加厚和山脉隆升过程,但是现有的变质记录主要为渐新世晚期-中新世中期,始新世变质作用的分布范围、形成过程和地质意义仍然未被充分挖掘。本文首先厘定了希夏邦马峰(8027m)山体的基本岩石组成:下部为高喜马拉雅正/副片麻岩,上部为肉切村群变粒岩及贯入其中的淡色花岗岩席。进一步对1964年希夏邦马峰登山科考采集的眼球状片麻岩进行了变质作用相平衡模拟和独居石微区原位U-Th-Pb定年,确定了始新世变质记录的P-T-t演化轨迹:M1阶段中P/T型变质压力峰期,条件为~1.0GPa、~740℃(~22℃/km),变质年龄为~37Ma;后近等温降压至M2阶段低P/T型变质温度峰期,条件为0.5~0.4GPa、~760℃(45~57℃/km),变质年龄为~25Ma;在~18Ma左右冷却至固相线以下。希夏邦马峰~37Ma的中P/T型变质和地壳加厚事件与北喜马拉雅穹隆、高喜马拉雅主体、前陆飞来峰等地区的记录一致(40~37Ma,20~25℃/km),表明印度-亚洲初始碰撞约20Myr后中上地壳被堆叠埋藏至>33km以下,发生了广泛的整体性加厚和深熔作用。该事件与喜马拉雅内陆残留海最终退却的时间吻合,是喜马拉雅山脉初始隆升的诱因。喜马拉雅山脉不是晚新生代以来隆升的,而是经历了自始新世中期以来的长期地壳堆叠和隆升过程。

习近平文化思想的哲学阐释

习近平文化思想是习近平新时代中国特色社会主义思想的重要组成部分,是新时代中国共产党领导文化建设实践经验的理论概括和科学总结。习近平文化思想深刻体现了新时代中国共产党人文化主体性的守正创新,以“两个结合”为深厚底蕴,坚持民族性与世界性相融通,将“魂脉”与“根脉”相结合,在认识论、历史观和辩证法层面实现了对马克思主义哲学的时代创新。习近平文化思想正面回应了西方文明的现代性困境,聚焦西方现代文明的自反性问题和价值异化倾向,提出构建人类命运共同体与创造人类文明新形态的科学论断。习近平文化思想坚持守正与创新相结合、坚持主体性与多样性相融汇、坚持理论与实践相贯通,在实践中深化了对中国特色社会主义文化建设规律的深刻认识,展现了习近平文化思想蕴含的哲学意蕴,必将在新时代中国特色社会主义文化建设中展现思想伟力,在担当新时代新的文化使命中彰显马克思主义的真理力量。

共建“一带一路”倡议下中国扩大教育对外开放十年实践审思

2023年是共建“一带一路”倡议提出十周年。十年来共建“一带一路”成为深受欢迎的国际公共产品和国际合作平台,极大地拓宽了包括教育在内的对外开放的深度与广度。在共建“一带一路”倡议下,中国教育对外开放取得显著成效,形成了教育对外开放的制度化框架、打造了较为完善的教育对外开放人才库、深化了教育对外开放的人文交流机制、扩大了中国教育国际公共产品供给。从“走出去”到“走进去”,共建“一带一路”倡议下的中国高水平教育对外开放应秉承构建人类命运共同体的理念逻辑,遵循以“文明、历史与世界”为主线的实践逻辑,通过优化共建“一带一路”教育合作新机制、拓展与“一带一路”共建国家教育发展新空间、精准服务人才中心和创新高地建设、拓展参与全球教育治理的广度与深度,开创共建“一带一路”倡议下中国扩大教育对外开放的第二个十年。

“一带一路”高等教育国际化智库建设研究

高等教育国际化智库是推动“一带一路”沿线国家高等教育国际化进程的重要思想库。该智库建设有助于推动“一带一路”高质量发展。“一带一路”高等教育国际化智库围绕“一带一路”高等教育改革与高等教育国际合作中的战略性、前瞻性、系统性问题开展战略研究和政策研究,是为“一带一路”高等教育国际化发展提供决策咨询的思想库。该智库承担着助推“一带一路”倡议的持续发展,服务构建“一带一路”高等教育共同体,以及培养高等教育国际化人才的使命。因此,“一带一路”高等教育国际化智库应具有包容互鉴、协同共建、互通互信、国际化、面向未来五个特征,并围绕以下四个着力点进行建设:一是明确发展理念,落实高等教育国际化智库的使命担当;二是秉持开放合作,搭建高等教育国际化合作框架;三是促进融合互通,共享高等教育发展资源;四是以质量为核心,提高高等教育国际化智库影响力。