Fracture behavior and mechanism of highly fragmented steel cylindrical shell under explosive loading

An in-depth understanding of the fracture behavior and mechanism of metallic shells under internal explosive loading can help develop material designs for warheads and regulate the quantity and mass distribution of the fragments formed.This study investigated the fragmentation performance of a new high-carbon silicon-manganese(HCSiMn)steel cylindrical shell through fragment recovery experiments.Compared with the conventional 45Cr steel shell,the number of small mass fragments produced by the HCSi Mn steel shell was significantly increased with a scale parameter of 0.57 g fitted by the Weibull distribution model.The fragmentation process of the HCSi Mn shell exhibited more brittle tensile fracture characteristics,with the microcrack damage zone on the outer surface being the direct cause of its high fragmentation.On the one hand,the doping of alloy elements resulted in grain refinement by forming metallographic structure of tempered sorbite,so that microscopic intergranular fracture reduces the characteristic mass of the fragments;on the other hand,the distribution of alloy carbides can exert a"pinning"effect on the substrate grains,causing more initial cracks to form and propagate along the brittle carbides,further improving the shell fragmentation.Although the killing power radius for light armored vehicles was slightly reduced by about 6%,the dense killing radius of HCSiMn steel projectile against personnel can be significantly increased by about 26%based on theoretical assessment.These results provided an experimental basis for high fragmentation warhead design,and to some extent,revealed the correlation mechanism between metallographic structure and shell fragmentation.

Patch occupancy by the Chinese Grouse(Tetrastes sewerzowi)in a fragmented landscape

The Chinese Grouse (Tetrastes sewerzowi) is a rare, endemic bird in China, inhabiting conifer-dominated mountain forests. Both the natural fragmentation and heavy cutting of mature forests have resulted in patchy grouse habitats. We used SPOT (XS-sensor) satellite imagery to discriminate between open land and conifer or broadleaf forests. The area analyzed is about 120000 ha in size and includes the Lianhuashan Nature Reserve and the Yeliguan Forestry Park. We identiifed 4111 ha of mature coniferous forests in 229 patches (maximum 332 ha, mean 18 ha) as the habitat used by Chinese Grouse throughout the year. We examined 31 forest islands of different sizes and degrees of isolation for the presence of Chinese Grouse. We used generalized linear models (GLM) with binomial error structure and logit link function to estimate the probability of Chinese Grouse occupancy in a forest fragment. Habitat patch size (hs) and distance to the next occupied fragment (doc) were used as predictor variables, important for occupancy. Small habitat islands were disproportionately less likely to be occupied than large, nearby habitats. There was a clear speciifc habitat size of about 40 ha, above which habitat fragments were occupied more often. Suitable habitat fragments isolated by more than 2 km appeared to be inaccessible to Chinese Grouse. The results have been used in reforestation projects to establish linking corridors in the study area.

Advantages and Disadvantages of Fragmented Learning and Recommendations

The development of information technology has changed people's learning methods. Fragmented learning,as an informal learning method,has become an important way to accept new knowledge and learn new technologies. Through analyzing the connotation,characteristics,and advantages and disadvantages of fragmented learning,this paper came up with reasonable recommendations for fragmented learning. To truly become systematic and holistic knowledge,fragmented knowledge must be explored,understood,integrated and internalized. This paper is expected to play an important guiding role in building a lifelong learning society.

β-diversity Patterns of Plant Community in Fragmented Habitat in a Degenerated Meadow in Songnen Plain,China

A number of isolated islands of Leymus chinensis ＋ herbosa community were investigated in fragmented habitat islands, by Braun-Blanquet field survey approach, in a degenerated meadow in the Songnen Plain, China in 2007. These islands were classified as large, medium, and small scales on the basis of the island area （100-1000m2, large island; 50-100m2, middle island; 10-50m2, small island）. Each scale of the investigation involved eight islands. The responses ofβ-diversity patterns of plant taxon to the habitat fragmentation at local community and metacommunity levels were analyzed on different scales of 24 isolated islands. The results indicated that at the local community level, there were 57 species belonging to 20 families and 49 genera in large islands, 49 species belonging to 16 families and 40 genera in middle islands, and 27 species belonging to eight families and 23 genera in small islands, β-diversity indexes for species, genus and family in large, middle, and small islands varied greatly, and the highest value of the indexes was not noted in the largest island. However, the average of the data obtained at the three scales showed that across large islands, Whittaker indexes were low and Bray-Curtis similarity indexes were high, while across small islands, Whittaker indexes were high and Bray-Curtis similarity indexes were low. At the metacommunity level, Whittaker indexes for species and genus showed a great significantly negative double logarithmic correlation （p〈0.01） with the island area, whereas the Bray-Curtis indexes for species, genus and family showed a great significantly positive double logarithmic correlation （p〈0.01） with the island area. At both local community and metacommunity levels, tumovers of species and genus could respond more sensitively to spatial changes of plant diversity patterns than that of family. Hence, the species and the genus could be used for the analysis offl-diversity patterns of plant community.

Idiopathic ventricular fibrillation with fragmented QRS complex and J wave in resting electrocardiogram

Objective To describe the clinical characteristics of idiopathic ventricular fibrillation （IVF） with fragmented QRS complex （f-QRS） and J wave in resting electrocardiogram. Methods We reviewed data from 21 case subjects in our hospital who were resuscitated after cardiac arrest due to IVF and assessed the prevalence of f-QRS and J wave in resting electrocardiogram （ECG）. All the case subjects were classified among three groups based on the electrocardiographic morphology： group I, both f-QRS and J wave were observed （n = 6）, group II, only J wave was observed （n = 9）, group III, neither f-QRS nor J wave was observed （n = 6）. Population characteristics, history of syncope or sudden cardiac arrest, incidence of ventricular fibrillation （VF）, and circumstance of VF were evaluated among the three groups. Results The incidence of index events （syncope, survived cardiac arrest and VF episodes recorded in implantable cardioverter defibrillator （ICD） or pacemakers） was 13.4 ~ 5.6 per-year in group I, 10.8 ~ 3.9 per-year in group II, and 9.8 -4- 4.2 per-year in group HI. There were significant differences in incidences among the three groups, the most frequent index events were observed in group I. The hazard ratio for incidence was 3.2 （95%CI, 1.1-7.9; P = 0.01）. The history and circumstance of the index events were different among the groups. In group I, all the index events occurred during sleep in early morning. In group II, four subjects suffered VF during strenuous physical activities or agitation state, two during sleep in early morning, three in usual activity. In group III, one subject suffered VF during sleep in early morning, one in agitation state, four in usual activity. Conclusions This study suggests that the IVF patients with the combined appearance of f-QRS and J wave in the resting ECG suffer an increased risk of VF, this subgroup of IVF patients has a unique clinical feature.

Influence of roads on small rodents population in fragmented forest areas, South Korea

The road effect on small rodent population is investigated at 8 fragmented forest areas in the Baekdudaegan mountain range, South Korea in September 2001. We especially focused on the distribution and body condition of small rodents near the roads. Korean field mouse (Apodemus peninsulae) seems to be more sensitive to the existence of a road than striped field mouse (Apodemus agrarius). Korean field mouse prefers interior forest area to around road. Striped field mouse is a habitat generalist and has wide distributional range around road, but Korean field mouse is forest-inhabiting species and their distribution is limited in forest area. These results suggest the effect of road is different on each small rodent species and their habitat preferences.

An assessment of population structure and regeneration status of Magnolia punduana Hk. f. & Th.(Magnoliaceae) in fragmented forests of northeast India

The population structure and regeneration status of Magnolia punduana Hk. f. & Th., an endemic tree species of northeast India were investigated in fragmented forests in the Jarain Hills and in adjoining areas of Meghalaya state. The population structure was discontinuous in all the fragments with the absence of individuals in higher diameter classes. The number of individuals increased with the size of the fragment patches(p < 0.004). The density of mature trees(≥5 cm dbh) was high(24–30 individuals ha-1) in the largest fragment(>105 ha). The number of seedlings and saplings were also higher in the larger fragments. Human-related disturbances had a negative impact on the species population(p<0.002). Variation in the population density in different forest patches has been attributed to fragment size, site characteristics and ongoing human disturbances. The restricted distribution of the species coupled withexploitation and habitat destruction underlines the need for its conservation.

Increased Prevalence of Severe Rheumatic Heart Disease Requiring Early Valve Replacement Surgery and Fragmented Germ Cells

Background: Patients requiring valve replacement at a younger age, for rheumatic heart disease was apparently increasing after the new age practice of contraception. Methods: In 2012, data of patients referred to tertiary care hospital from two cardiology screening camps conducted in the community, were analyzed for the severity of presentation of rheumatic heart disease and associated contraception status by dividing into the three age groups—20 - 35 years, 36 - 50 years, >51 years;~400 patients attended the camps;31 female and 2 male patients were referred to the tertiary care hospital for further evaluation and categorized treatment, including valve replacement surgeries;among the 33 referred patients, belonging to the three age groups, the data were analyzed for [if any] correlation of contraception status with severe rheumatic heart disease. 8 randomly chosen males, of the 3 age groups, from a different community, whose life partners had undergone sterilization, were assessed for their serum testosterone levels. Results: Among 20 - 35 years, 7 female patients with contraception required valve replacement surgeries [p 51 years, 3 female and 2 male patients without contraception received medical treatment only

Influencing Factors of Seed Long-distance Dispersal on a Fragmented Forest Landscape on Changbai Mountains,China

Seed long-distance dispersal(LDD) events are typically rare, but are important in the population processes that determine large-scale forest changes and the persistence of species in fragmented landscapes. However, previous studies focused on species dispersed via animal-mediated LDD, and ignored those dispersed by wind. The aim of this study was to assess the effects of canopy openness, edge, seed source, and patch tree density on the LDD of seeds by wind in forest. We collected birch seeds, a typical wind-dispersed species, throughout a larch plantation. We then assessed the relationship between birch LDD and each factor that may influence LDD of seeds by wind including distance to edge, canopy openness size, distance to mature forest, and the tree density of the larch plantation. We used univariate linear regression analysis to assess the influence of those factors on birch LDD, and partial correlations to calculate the contribution of each factor to LDD. The results showed that both canopy openness and edge had significant influences on birch LDD. Specifically, a negative relationship was observed between distance to edge and birch LDD, whereas there was a positive correlation between canopy openness size and LDD. In contrast, the distance to the mature forest was not correlated with birch LDD. Our results suggest that patch tree density could potently affect the probability of LDD by wind vectors, which provides novel and revealing insights regarding the effect of fragmentation on wind dynamics. The data also provide compelling evidence for the previously undocumented effect of habitat fragmentation on wind-dispersed organisms. As such, these observations will facilitate reasonable conservation planning, which requires a detailed understanding of the mechanisms by which patch properties hamper the delivery of seeds of wind-dispersed plants to fragmented areas.

基于Fragmented Learning的中医药高效学习软件——“我药学”手机APP设计实现

基于Fragmented Learning的中医药高效学习软件——"我药学"手机APP通过手机解锁记忆中医药知识,充分利用了学生日常生活中碎片化的时间,帮助记忆枯燥的学习内容,大大提高了学生的学习兴趣和学习效率,最终解决中医药知识记忆难的难题。

Importance of microhabitat selection by birds for the early recruitment of endangered trees in a fragmented forest

Background:Remnant microhabitats are important for bird habitat selection and plant regeneration in the fragmented habitat.However,empirical information on the consequences of how microhabitat use by birds affects the early recruitment of plants is lacking.Methods:In this study,we evaluated whether microhabitat selection by the Black Bulbul(Hypsipetes leucocephalus)(J.F.Gmelin,1789)impacts the early recruitment of the endangered tree species,the Chinese Yew(Taxus chinensis(Pilger)Rehd),in a fragmented forest over a 4-year period(2011–2012,2018–2019).Results:Our results showed the main factors affecting H.leucocephalus microhabitat selection were distance to the nearest T.chinensis mature tree,herb cover and density,leaf litter cover,and vegetation type.Moreover,the results of logistic regression also highlighted the importance of elevation,distance to light gap and roads,tree cover in bird microhabitat selection.Furthermore,the seed emergence rate in microhabitats used by birds did not differ from the natural forest,which was related to five factors of bird microhabitat.The Random Forest model showed that seedling emergence rate was increased with leaf litter cover and distance to fallen dead trees,but decreased in relation to herb cover,slope,and elevation.Conclusion:Our results highlight the importance of remnant microhabitats in fragmented forests for sustaining forest ecology and optimal management.The contribution of microhabitats used by birds to plant recruitment provides insights into how frugivore species contribute to plant regeneration,which should be incorporated in future conservation and management practices of fragmented forests.

How Does China Impact the Future International Political Order？ Conceptual Reflections of the ＂China Model＂ in Light of China＇s Fragmented Polity

This article ties in with the research on an emerging ＂China model＂ as an alternative to conceptions of political order introduced and promoted by the ＂West＂. While the term ＂China model＂ will remain of enormous political importance and is in need of further research, the emergence of a ＂one size fits all＂ model of Chinese policy making is rather unlikely. Instead of searching for such a model, social scientific research should analyze whether and how the fragmented Chinese polity is being impacted by such unitary ＂ideas＂ of a Chinese political order and vice versa.

Fragmented People in the Fragmented Country in Midnight's Children:Viewed from the Perspective of “Fragmentation”

In Midnight's Children,frequently seen are the words like"hole","segment","crack",and the damage and loss of bodily function such as amnesia,which is called a"phenomenon of fragmentation"in this paper.In terms of the phenomenon,the characters of three generations in Midnight's Children are analyzed.It is found that colonial culture exerts a long-lasting impact on its colonized people,under whose influence generations of colonized people find it hard to negotiate their dual cultural identities.This happened to India.Postcolonial Indians had fragmented identities.Furthermore,the phenomenon also reflects that India was a fragmented nation,whose nationals desired peace,unity,and prosperity.

Fragmented forest in tropical landscape——the case of the State of Selangor, Malaysia

This paper presents the pattern and changes of fragmented forest in relation with changes of total forest cover in the state of Selangor in three decades. In this study, inventoried forest cover maps of Selangor in 1971/1972, 1981/1982 and 1991/1992 produced by the Forestry Department of Peninsular Malaysia were digitized to examine the changes in area and number of fragmented forest. Results showed that in 1971/1972, 16 fragmented forests were identified in Selangor. All fragmented forests were identified as dipterocarp forest. A decade later the number of fragmented forests increased by approximately 44% (23). Of the 23 fragmented forests, two were peat swamp forests whereas the remaining were dipterocarp forests. In 1991/1992 the number of fragmented forests (12) was reduced by 47.8%. Two of the fragmented forests were identified as peat swamp forest, seven dipterocarp forest and the other three was mixed of dipterocarp forests and plantation forests. Fragmentation of both dipterocarp and peat swamp forests occurred profoundly during the period between 1971/1972 and 1981/1982, which consequently increased the number of fragmented forests compared with before the period of 1971/1972 where fragmentation happened only at dipterocarp forests. However, many fragmented forests vanished between the 1981/1982 and 1991/1992 periods.

Seed dispersal by Tana River mangabeys in fragmented gallery forests

Data collected on a free ranging group of Tana River mangabeys (Cercocebus galeritus) indicates that this endangered primate species, which has previously been regarded as a seed predator, plays an important role in seed dispersal and do contribute to the regeneration of a highly fragmented gallery forest. We observed fruit handling behavior and the post-dispersal fate of seeds ingested by the mangabeys. The two main fruit handling behaviors observed, fruit swallowing and processing fruits in cheek pouches, positively contributed to seed disper- sal. Seed predation was not common during this study, apart from a few particular plant species such as Acacia robusta and Alangium salviifolium with non-fleshy fruits. We found a correlation between seed predation and fruit availability, respectively seasonal differential specific dispersal efficiency. The role of the mangabeys in dispersing seeds and facilitating forest regeneration is enhanced by their movement across forest patches through non-forested matrix, which contributes to the deposition of seeds and regeneration in these habitat gaps.

Enhancing rock fragmentation prediction in mining operations:A hybrid GWO-RF model with SHAP interpretability

In the mining industry,precise forecasting of rock fragmentation is critical for optimising blasting processes.In this study,we address the challenge of enhancing rock fragmentation assessment by developing a novel hybrid predictive model named GWO-RF.This model combines the grey wolf optimization(GWO)algorithm with the random forest(RF)technique to predict the D_(80)value,a critical parameter in evaluating rock fragmentation quality.The study is conducted using a dataset from Sarcheshmeh Copper Mine,employing six different swarm sizes for the GWO-RF hybrid model construction.The GWO-RF model’s hyperparameters are systematically optimized within established bounds,and its performance is rigorously evaluated using multiple evaluation metrics.The results show that the GWO-RF hybrid model has higher predictive skills,exceeding traditional models in terms of accuracy.Furthermore,the interpretability of the GWO-RF model is enhanced through the utilization of SHapley Additive exPlanations(SHAP)values.The insights gained from this research contribute to optimizing blasting operations and rock fragmentation outcomes in the mining industry.

Numerical and experimental investigation on hydraulic-electric rock fragmentation of heterogeneous granite

Hydraulic-electric rock fragmentation(HERF)plays a significant role in improving the efficiency of high voltage pulse rock breaking.However,the underlying mechanism of HERF remains unclear.In this study,considering the heterogeneity of the rock,microscopic thermodynamic properties,and shockwave time domain waveforms,based on the shockwave model,digital imaging technology and the discrete element method,the cyclic loading numerical simulations of HERF is achieved by coupling electrical,thermal,and solid mechanics under different formation temperatures,confining pressure,initial peak voltage,electrode bit diameter,and loading times.Meanwhile,the HERF discharge system is conducive to the laboratory experiments with various electrical parameters and the resulting broken pits are numerically reconstructed to obtain the geometric parameters.The results show that,the completely broken area consists of powdery rock debris.In the pre-broken zone,the mineral cementation of the rock determines the transition of type CⅠcracks to type CⅡand type CⅢcracks.Furthermore,the peak pressure of the shockwave increased with initial peak voltage but decreased with electrode bit diameter,while the wave front time reduced.Moreover,increasing well depth,formation temperature and confining pressure augment and inhibit HERF,but once confining pressure surpassed the threshold of 60 MPa for 152.40,215.90,and 228.60 mm electrode bits,and 40 MPa for 309.88 mm electrode bits,HERF is promoted.Additionally,for the same kind of rock,the volume and width of the broken pit increase with higher initial peak voltage and rock fissures will promote HERF.Eventually,the electrode drill bit with a 215.90 mm diameter is more suitable for drilling pink granite.This research contributes to a better microscopic understanding of HERF and provides valuable insights for electrode bit selection,as well as the optimization of circuit parameters for HERF technology.

Application Research of Fragmented Case Teaching in Standardized Training of Residents in Anesthesiology Department

Objective:To explore the effect of fragmented case teaching in the standardized training of residents in anesthesiology department.Methods:80 doctors who participated in the standardized training of residents in anesthesiology department from January 2021 to January 2022 were selected as the research objects,and the 80 doctors were divided into experimental groups according to the clinical teaching mode(n=40,implemented case fragmented teaching method)and the control group(n=40,traditional teaching method).The training lasted for 2 months,and the medical history collection,medical record analysis,practical operation ability,theoretical assessment results,and the degree of satisfaction towards the training of the two groups of doctors were compared.Results:After 2 months of training,the theoretical knowledge and operational ability of the doctors in the two groups have improved to a certain extent,but the medical history collection,medical record analysis,practical operation ability,theoretical assessment results and satisfaction of the doctors in the experimental group were significantly better than those in the control group(P<0.05).Conclusion:The effect of the fragmented case teaching method in the standardized training of anesthesiology residents is significantly better than the traditional teaching mode.The abilities of doctors have significantly improved after the training.Hence,the fragmented case teaching method is worthy of promotion in clinical practice.

An Analysis of Fragmented Reading and Its Social Impact on College Students in the Era of New Media

In the era of new media,people’s lifestyle,education and the like are inseparable from the Internet.At the same time,due to the emergence of smart devices such as mobile phones and tablet computers,people’s reading habits have changed.Fragmented reading has become an important form of reading for college students.College students themselves have the strong ability to accept change,so fragmented reading has gradually become an important form of student learning.This paper mainly analyses fragmented reading by college students and its impact on society in the era of new media.

Feasibility Investigation and Development Exploration on Popularizing the Method of English Fragmented Mobile Learning of Undergraduates

This paper attempts to investigate the feasibility and learning effects of English fragmented learning via mobile devices.Questionnaires and interviews were employed to do the survey on 157 undergraduates from 24 universities in China.The research findings reveal that English fragmented learning via mobile devices has some positive effects on the improvement of learners’knowledge and learning ability.In addition,there have been a certain number of useful learning resources and platforms with diversified features.The study has the implications that fragmented mobile learning is feasible and can be popularized in English learning.