期刊文献+
共找到1,727篇文章
< 1 2 87 >
每页显示 20 50 100
Study of Neutron Cross Talk Rejection Based on Testing Experiment and Simulation
1
作者 游海波 宋玉收 +1 位作者 肖军 叶沿林 《Plasma Science and Technology》 SCIE EI CAS CSCD 2012年第6期473-477,共5页
Experimental data analysis and simulation calculations were performed in order to evaluate the cross-talk rejection performance of a typical neutron detection array. For very closely packed scintillation bars, the CT ... Experimental data analysis and simulation calculations were performed in order to evaluate the cross-talk rejection performance of a typical neutron detection array. For very closely packed scintillation bars, the CT rejection may rely on the position relation between the two signals. The criteria |△x|≤ 15 cm and |△y|≤12 cm are currently proposed for a rejection rate higher than 90%. For signals coming from distanced bars, the energy conservation relationship can be applied to reject the CT events with a similar performance. In both cases the results of simulation agree very well with the experimental data, assuring their applicability to other detection systems and physics problems. 展开更多
关键词 test experiment GEANT4 simulation cross talk neutron detection
下载PDF
On the Analysis Method of the Triple Test Cross Design
2
作者 Jin Yi(Northeast Agricultural University, Harbin 1 50030, P R C) 《Journal of Northeast Agricultural University(English Edition)》 CAS 1995年第1期66-74,共9页
The analysis method of the triple test cross design has been discussed carefully from the two factor experiment design and the genetic models of additive dominant effect and of epistasis effect.Two points different f... The analysis method of the triple test cross design has been discussed carefully from the two factor experiment design and the genetic models of additive dominant effect and of epistasis effect.Two points different from the previous reports have been concluded: (1)both the degrees of freedom of the orthogonal terms C2 and C3 are m, (2)the denominator in the F test to C2 and C3 is the error mean of square between plots. 展开更多
关键词 Triple test cross design Additive-dominant model Epistasis model Genetic parameter estimate.
下载PDF
Characteristics of the Variation of Cross Fault Short-Baseline and Short-Range Leveling in Western Yunnan Earthquake Test Site Before Lijiang M_S7.0 Earthquake
3
作者 Li Zhonghua, Su Youjing, and Liu ZhuyinSeismological Bureau of Yunnan Province, Kunming 650041, China 《Earthquake Research in China》 1998年第4期46-56,共11页
Results of analysis of variation of cross fault short-baseline and short-range leveling in Western Yunnan Earthquake Test Site (WYETS), results show that among five observation stations of cross fault short-baseline a... Results of analysis of variation of cross fault short-baseline and short-range leveling in Western Yunnan Earthquake Test Site (WYETS), results show that among five observation stations of cross fault short-baseline and short-range leveling in WYETS before the Lijiang MS7.0 Earthquake occurred in February 1996 only Yongsheng observation station (epicentral distance 82 km) located at Chenghai fault shows great variation about one year before the earthquake. And the nearest observation station, Lijiang (epicentral distance 42 km); presents great coseismic variation, but does not show obvious anomalous variation before the earthquake. There are no significant variations related to the earthquake at the other three observation stations. Two methods are used in analysis of the observed data and some valuable results have been obtained. 展开更多
关键词 cross FAULT measurement Lijiang MS7.0 EARTHQUAKE Western Yunnan EARTHQUAKE test Site.
下载PDF
Research and application of cross-test strategy based on component
4
作者 SONG Yu TIAN Hua CAO Yong-feng 《通讯和计算机(中英文版)》 2007年第8期40-43,共4页
关键词 交叉测试策略 软件测试 组成 应用 软件开发
下载PDF
Self-Cross-Linked Tannin-Aminated Tannin Surface Coatings for Particleboard
5
作者 Bengang Zhang Antonio Pizzi +2 位作者 Mathieu Petrissans Anelie Petrissans Colin Baptiste 《Journal of Renewable Materials》 EI 2023年第12期4097-4121,共25页
Aminated tannins were prepared by reacting mimosa condensed tannin extract with ammonia yielding the substitution of many,if not all of the tannin hydroxyl groups with–NH_(2)groups.A tannin-aminated tannin(ATT)partic... Aminated tannins were prepared by reacting mimosa condensed tannin extract with ammonia yielding the substitution of many,if not all of the tannin hydroxyl groups with–NH_(2)groups.A tannin-aminated tannin(ATT)particleboard coating was then prepared by reacting raw tannin extract with aminated tannin extract and thus cross-linking the two by substituting tannin’s hydroxyl groups with the–NH_(2)groups on the aminated tannin to form–NH-bridges between the two.The resulting particleboard coating gave encouraging results when pressed at 180℃for 3 min.Conversely,the system in which tannin was reacted/cross-liked with urea(ATU)by a similar amination reaction did not perform as well as the ATT system,and this even when a higher curing temperature and longer hot press time were used.In particular its water repellence was worse probably due to the presence of urea and such a system with lower reactivity.Nonetheless,substituting the tannin–OHs with the urea–NH_(2)groups appeared to also take place.ATT gave better results than ATU as regards water repellence and mechanical resistance as shown by the cross cut test.The ATT system was shown to be between 95%and 98%biosourced.The difference appeared to be due,by TMA analysis,to the much faster formation of the ATT hardened network leading to a better cross-linked polymer coating.The chemical species formed for both the ATT and ATU system were studied by MALDI ToF and CP MAS^(13)C NMR. 展开更多
关键词 Biocoatings PARTICLEBOARD aminated tannin cross-linked tannin-aminated tannin tannin-urea cross links water repellence cross cut test MALDI ToF ^(13)C NMR
下载PDF
The “Colour Family Drawing Test”: Assessing Children’s Perception of Family Relationships. Studies on Mental Health and Cross-Cultural Comparisons
6
作者 Valeria Biasi Paolo Bonaiuto James M. Levin 《Health》 2015年第3期300-307,共8页
We apply the Colour Family Drawing Test, as a development of the traditional black and white test, for cross-cultural comparison. The participants, aged 7 - 10 years, both genders, were examined individually. Each sub... We apply the Colour Family Drawing Test, as a development of the traditional black and white test, for cross-cultural comparison. The participants, aged 7 - 10 years, both genders, were examined individually. Each subject sat at a single table with a white rectangular card of standard size, 24 well-sharpened colour pencils, a black pencil, an eraser and other appropriate tools. S/he received this verbal instruction: “Draw your family”. The procedure was firstly applied to 120 participants attending primary schools of Rome (Biasi, Bonaiuto and Levin, 2014). The families were evaluated through a semi-structural interview conducted with the children’s teachers and divided into: Harmonious versus Very Conflictual Families. The drawings made by children of Harmonious Families consistently used “Reassuring and Playful Colours” (Pink, Orange, Sky Blue, Light Green, Light Yellow, other pastel colours);and were larger, tidier and more proportioned to respect the opposite group. Children belonging to Conflictual Families used mostly “Alarming and Serious Colours” (Grey, Black, Dark Bleu, Violet, Olive Green) and their drawings were less extended, more often disordered and had typical deformations such as figures too thin. A second investigation examined 120 participants belonging to Asian immigrant families residing in Italy. A third investigation examined 120 participants belonging to Russian families of Moscow. Both last two investigations obtained very similar results on the use of colours, and gave a confirmation of the relevance of the Colour Family Drawing Test. 展开更多
关键词 COLOUR Conflictual FAMILY cross-Cultural Comparison COLOUR DRAWING FAMILY test EXPRESSIVENESS
下载PDF
Testing for Cross-Sectional Dependence in a RandomEffects Model
7
作者 Afees Salisu Sam Olofin Eugene Kouassi 《Open Journal of Statistics》 2012年第1期88-97,共10页
This paper extends and generalizes the works of [1,2] to allow for cross-sectional dependence in the context of a two-way error components model and consequently develops LM test. The cross-sectional dependence follow... This paper extends and generalizes the works of [1,2] to allow for cross-sectional dependence in the context of a two-way error components model and consequently develops LM test. The cross-sectional dependence follows the first order spatial autoregressive error (SAE) process and is imposed on the remainder disturbances. It is important to note that this paper does not consider alternative forms of spatial lag dependence other than SAE. It also does not allow for endogeneity of the regressors and requires the normality assumption to derive the LM test. 展开更多
关键词 cross-SECTIONAL DEPENDENCE Error Components MODEL LAGRANGIAN MULTIPLIER (LM) tests
下载PDF
Research on Well Testing Interpretation of Low Permeability Deformed Dual Medium Reservoir
8
作者 Meinan Wang Yue Xie +2 位作者 Rui Zhang Guohao Zhang Jianguo Liu 《Open Journal of Applied Sciences》 2023年第11期2141-2148,共8页
Considering the influence of quadratic gradient term and medium deformation on the seepage equation, a well testing interpretation model for low permeability and deformation dual medium reservoirs was derived and esta... Considering the influence of quadratic gradient term and medium deformation on the seepage equation, a well testing interpretation model for low permeability and deformation dual medium reservoirs was derived and established. The difference method was used to solve the problem, and pressure and pressure derivative double logarithmic curves were drawn to analyze the seepage law. The research results indicate that the influence of starting pressure gradient and medium deformation on the pressure characteristic curve is mainly manifested in the middle and late stages. The larger the value, the more obvious the upward warping of the pressure and pressure derivative curve;the parameter characterizing the dual medium is the crossflow coefficient. The channeling coefficient determines the time and location of the appearance of the “concave”. The smaller the value, the later the appearance of the “concave”, and the more to the right of the “concave”. 展开更多
关键词 Low Permeability Oil Reservoirs Deformation Medium Dual Media cross Flow Coefficient Well testing Interpretation Model
下载PDF
一种基于函数依赖的跨合约模糊测试方案
9
作者 张立强 路梦君 严飞 《信息网络安全》 CSCD 北大核心 2024年第7期1038-1049,共12页
随着区块链应用的快速发展和智能合约的广泛使用,由智能合约引发的安全事件急剧增多,导致基于区块链的数字资产产生了巨大损失。目前,虽然部分工具可以检测智能合约安全漏洞,但是它们主要针对单个智能合约进行检测,未考虑跨合约之间的... 随着区块链应用的快速发展和智能合约的广泛使用,由智能合约引发的安全事件急剧增多,导致基于区块链的数字资产产生了巨大损失。目前,虽然部分工具可以检测智能合约安全漏洞,但是它们主要针对单个智能合约进行检测,未考虑跨合约之间的交互依赖关系,因此会产生较多的误报。针对上述智能合约漏洞检测工具在跨合约场景下误报率较高和性能消耗过大的问题,文章提出一种基于函数依赖的跨合约模糊测试方案FIFuzz。该方案提出ContractRank算法进行合约间依赖关系建模,采用函数重要度来表征函数在合约间交互过程中的重要程度,并在后续模糊测试模块中加以利用。模糊测试通过基于函数重要度的交易序列生成策略和基于合约地址映射关系的地址类型数据生成策略来提高检测效率,缩减跨合约漏洞检测的搜索空间。另外,通过合约调用模拟来降低漏洞检测的假阳性率。与相关工具的对比实验表明,FIFuzz的漏洞检测时间相对其他工具缩短了80%,检测到的漏洞数量是其他工具的两倍,检测跨合约漏洞的准确率也明显高于其他工具。实验结果表明,FIFuzz能够有效提升跨合约漏洞的检测准确率,降低误报率,并减小时间开销。 展开更多
关键词 智能合约 模糊测试 跨合约漏洞
下载PDF
Lung Function Impairment among Gasoline Attendants: A Cross-Sectional Study
10
作者 Emmanuel Obazee Henry Aiwuyo +8 位作者 Anthony Kweki Tinuade Obazee Tinuade Obazee John Osarenkhoe Uche Agboje Beatrice Torere Nosakhare Ilerhunmwuwa Uchenna Amaechi Gabriel Alugba 《Open Journal of Ecology》 2023年第3期48-63,共16页
Background: Occupational health is an important consideration, especially for people that work in an environment with pollutants. Gasoline attendants are individuals that work in filling stations. They are constantly ... Background: Occupational health is an important consideration, especially for people that work in an environment with pollutants. Gasoline attendants are individuals that work in filling stations. They are constantly exposed to gasoline fumes and automobile engine products from vehicle exhaust. This increases the risk of acute and chronic respiratory diseases and carcinogenesis among them. The risk of health complications tends to increase with the duration of exposure. The study aimed to determine the proportion of gasoline attendants with lung function impairment. Methods and Materials: Two hundred and eight eligible participants were recruited for this study. A cross-sectional analytical study was carried out in Esan West local government area of Edo state, Nigeria. The study was carried out for a period of six months from December 2015 to May 2016. A questionnaire was used to obtain information on demographic characteristics, work history, mode of exposure and duration of exposure to petrol fumes. Lung function was assessed using a DTspiro spirometer (Model POP 10. Serial no 110843-005);also the anthropometric parameters of the respondent were measured. Statistical analysis was done using IBM SPSS version 20.0. Frequency and percentages were used to present categorical data. The mean and standard deviation of continuous variables were calculated and compared using the student’s t-test. The criteria of significant association were assumed for a p-value less than 0.05. Results: A total of one hundred and forty petrol pump attendants and one hundred and forty controls participated in this study. The mean age for petrol pump attendants was 24 ± 3.1 years and 23 ± 2.8 years for the control group. There were no significant differences in the gender distribution and anthropometric parameters as observed in this study. The lung impairment pattern observed in this study was obstructive in twelve (8.6%) gasoline pump attendants and restrictive pattern in thirty-nine (27.9%) gasoline pump attendants, while only four (2.9%) had an obstructive pattern and twelve (8.6%) had a restrictive pattern of lung impairment among the control group. This implies that a restrictive pattern was predominant. This study also observed that there was an increase in the number of gasoline pump attendants with declined lung function compared to the control group. Conclusion: Restrictive pattern of lung impairment was more predominant than the obstructive pattern among gasoline pump attendants. As a result, public health interventions should be instituted among these individuals, especially in developing countries. 展开更多
关键词 Lung Function test Lung Impairment Lung Impairment Pattern Gasoline Attendants Occupational Hazards cross-Sectional Study
下载PDF
复杂受荷下盾构隧道原型结构试验平台的研发与实证
11
作者 柳献 刘震 +1 位作者 叶宇航 姚鸿梁 《岩土工程学报》 EI CAS CSCD 北大核心 2024年第5期927-937,共11页
盾构隧道结构在全寿命周期中往往将面临诸多复杂荷载状态,如注浆、偏载、偏转等非对称偏不利工况。为验证结构在这些复杂荷载状态下的适用性,探究结构力学性能,开展足尺原型结构试验研究往往是最为直接而有效的手段。既有原型试验主要... 盾构隧道结构在全寿命周期中往往将面临诸多复杂荷载状态,如注浆、偏载、偏转等非对称偏不利工况。为验证结构在这些复杂荷载状态下的适用性,探究结构力学性能,开展足尺原型结构试验研究往往是最为直接而有效的手段。既有原型试验主要关注隧道结构在简单对称荷载条件下的力学性能,鲜有关注复杂非对称荷载状态。为拓展原型试验的适用范围,提出了适用于不同断面盾构隧道结构的原型试验平台和用于模拟复杂荷载状态的试验荷载设计方法。该方法适用于任意加载点布置和液压站分组的试验系统,可对注浆、偏载、偏转等复杂荷载状态下结构响应进行精确模拟。通过类矩形盾构隧道、双圆隧道和圆形隧道的偏载原型结构试验研究,验证了试验平台和试验荷载设计方法的适用性。进一步针对试验关键参数的分析表明,控制目标权重系数的调整能有效满足不同的试验模拟要求;基于试验荷载设计方法优化的迭代算法能有效考虑计算模型或边界支承条件的非线性;环箍钢绞线和千斤顶的组合加载模式能将拟合误差水平降低至千斤顶加载模式的1/5,但需要删去部分加载点使试验荷载合理且适用;对于越复杂的结构和荷载,精确模拟结构状态需要的试验系统独立荷载组数越高,对试验平台的要求也越高。 展开更多
关键词 复杂受荷状态 原型试验 试验平台 试验荷载设计 断面形式
下载PDF
Lung Function Impairment among Gasoline Attendants: A Cross-Sectional Study
12
作者 Emmanuel Obazee Henry Aiwuyo +8 位作者 Anthony Kweki Tinuade Obazee Tinuade Obazee John Osarenkhoe Uche Agboje Beatrice Torere Nosakhare Ilerhunmwuwa Uchenna Amaechi Gabriel Alugba 《Open Journal of Respiratory Diseases》 2023年第3期48-63,共16页
Background: Occupational health is an important consideration, especially for people that work in an environment with pollutants. Gasoline attendants are individuals that work in filling stations. They are constantly ... Background: Occupational health is an important consideration, especially for people that work in an environment with pollutants. Gasoline attendants are individuals that work in filling stations. They are constantly exposed to gasoline fumes and automobile engine products from vehicle exhaust. This increases the risk of acute and chronic respiratory diseases and carcinogenesis among them. The risk of health complications tends to increase with the duration of exposure. The study aimed to determine the proportion of gasoline attendants with lung function impairment. Methods and Materials: Two hundred and eight eligible participants were recruited for this study. A cross-sectional analytical study was carried out in Esan West local government area of Edo state, Nigeria. The study was carried out for a period of six months from December 2015 to May 2016. A questionnaire was used to obtain information on demographic characteristics, work history, mode of exposure and duration of exposure to petrol fumes. Lung function was assessed using a DTspiro spirometer (Model POP 10. Serial no 110843-005);also the anthropometric parameters of the respondent were measured. Statistical analysis was done using IBM SPSS version 20.0. Frequency and percentages were used to present categorical data. The mean and standard deviation of continuous variables were calculated and compared using the student’s t-test. The criteria of significant association were assumed for a p-value less than 0.05. Results: A total of one hundred and forty petrol pump attendants and one hundred and forty controls participated in this study. The mean age for petrol pump attendants was 24 ± 3.1 years and 23 ± 2.8 years for the control group. There were no significant differences in the gender distribution and anthropometric parameters as observed in this study. The lung impairment pattern observed in this study was obstructive in twelve (8.6%) gasoline pump attendants and restrictive pattern in thirty-nine (27.9%) gasoline pump attendants, while only four (2.9%) had an obstructive pattern and twelve (8.6%) had a restrictive pattern of lung impairment among the control group. This implies that a restrictive pattern was predominant. This study also observed that there was an increase in the number of gasoline pump attendants with declined lung function compared to the control group. Conclusion: Restrictive pattern of lung impairment was more predominant than the obstructive pattern among gasoline pump attendants. As a result, public health interventions should be instituted among these individuals, especially in developing countries. 展开更多
关键词 Lung Function test Lung Impairment Lung Impairment Pattern Gasoline Attendants Occupational Hazards cross-Sectional Study
下载PDF
液化场地大直径变截面单桩动力响应研究
13
作者 冯忠居 段久琴 +3 位作者 张聪 林立华 赵瑞欣 王逸然 《湖南大学学报(自然科学版)》 EI CAS CSCD 北大核心 2024年第5期56-67,共12页
为研究不同地震动强度下液化场地大直径变截面单桩的动力响应规律,基于振动台试验,选取5010波,在地震动强度0.10g~0.45g作用下,研究液化场地砂土孔压比和大直径变截面单桩桩顶水平位移、桩身弯矩、桩身加速度时程响应及桩基损伤等变化规... 为研究不同地震动强度下液化场地大直径变截面单桩的动力响应规律,基于振动台试验,选取5010波,在地震动强度0.10g~0.45g作用下,研究液化场地砂土孔压比和大直径变截面单桩桩顶水平位移、桩身弯矩、桩身加速度时程响应及桩基损伤等变化规律.试验结果表明:饱和砂土孔压比随着地震动强度的增大上升明显,地震动强度≥0.30g时,饱和砂土孔压比稳定值在0.9附近,此时砂土完全液化;在0.45g地震动强度作用下,桩身加速度、桩顶水平位移及桩身弯矩均达到最大;桩身不同位置处加速度峰值出现时刻均滞后于输入地震波加速度峰值出现时刻,且桩顶及变截面的加速度响应比桩端的响应更弱;不同地震动强度作用下,桩身弯矩最大值均出现在液化土层和非液化土层分界处,且变截面处弯矩小于土层分界面处;地震动强度达到0.30g时,大直径变截面单桩桩身发生损伤.因此,液化场地下大直径变截面桥梁单桩基础抗震设计时,应该重点考虑饱和砂土层分界处、变截面处的抗弯能力,以确保单桩桩身强度满足抗震要求. 展开更多
关键词 岩土工程 变截面单桩 液化场地 动力响应 振动台试验 抗震设计
下载PDF
胀锁型锚索双向加固窄煤柱试验研究与工程应用
14
作者 王军 吕顺章 +3 位作者 杨光 王波 谷长宛 王港 《矿业科学学报》 CSCD 北大核心 2024年第2期258-269,共12页
针对沿空掘巷窄煤柱非对称变形问题,提出了对穿锚索双向加固窄煤柱技术,设计了伸长型和胀锁型两种对穿锚索结构及工艺,开展了对穿锚索拉拔试验,试验表明两种锚索结构均满足抗拉要求,从锚索破坏形态、施工便捷性和材料经济性等方面对比分... 针对沿空掘巷窄煤柱非对称变形问题,提出了对穿锚索双向加固窄煤柱技术,设计了伸长型和胀锁型两种对穿锚索结构及工艺,开展了对穿锚索拉拔试验,试验表明两种锚索结构均满足抗拉要求,从锚索破坏形态、施工便捷性和材料经济性等方面对比分析,确定胀锁型对穿锚索为窄煤柱双向加固的首选。进一步通过相似模型试验与数值模拟研究了不同加固方式下煤柱承载变形规律和对穿锚索受力特征。结果表明:双排紧密型对穿锚索加固试件较未加固试件峰值荷载提高了96.04%,且随着锚索排数及数量的增加,窄煤柱双向加固稳定性越来越高,胀锁型对穿锚索提高了煤柱破坏前的能量储存量和临界破坏点。最后,在济宁三号煤矿123_(下)04工作面运输巷开展胀锁式对穿锚索加固窄煤柱工程试验,监测显示对穿锚索锚固力超过220 kN,锚索加固区煤柱帮鼓量降低70%,窄煤柱整体稳定性好,窄煤柱双向加固技术可行,为沿空掘巷工程提供了新技术途径。 展开更多
关键词 沿空掘巷 双向加固 窄煤柱 胀锁型对穿锚索 拉拔试验 承压性能
下载PDF
输电铁塔装配式基础抗剪键连接的剪切性能
15
作者 吕庆 胡嘉飞 +2 位作者 麻坚 华献宏 徐刚 《浙江大学学报(工学版)》 EI CAS CSCD 北大核心 2024年第6期1153-1160,共8页
预制构件连接方法及其界面剪切性能影响整个输电铁塔装配式基础的受力和变形.针对螺栓连接易松动、变形大之类的问题,提出采用高强灌浆料灌注成形的十字形抗剪键作为输电铁塔装配式基础连接方案.采用室内剪切试验和数值模拟,研究该抗剪... 预制构件连接方法及其界面剪切性能影响整个输电铁塔装配式基础的受力和变形.针对螺栓连接易松动、变形大之类的问题,提出采用高强灌浆料灌注成形的十字形抗剪键作为输电铁塔装配式基础连接方案.采用室内剪切试验和数值模拟,研究该抗剪键连接的剪切性能,并与常用的螺栓连接进行对比分析.结果表明:十字形抗剪键剪切破坏模式为剪断型脆性破坏,破坏形态表现为以抗剪键为中心向外略有扩展成菱形.和螺栓连接相比,抗剪键连接的剪切强度略低,但剪切刚度显著提高.浇筑过程中灌浆料外溢对界面抗剪强度有提高作用.抗剪键的抗剪性能与灌浆料强度正相关,但提高灌浆料强度对抗剪性能提升并不明显.抗剪键深度对抗剪性能有影响,但在抗剪键深度超过20 mm后,抗剪键的抗剪性能不再提高.根据剪切试验和数值模拟结果,建议十字形抗剪键设计为长200 mm、宽20 mm、深20 mm. 展开更多
关键词 输电铁塔 装配式基础 十字形抗剪键 剪切性能 剪切试验
下载PDF
跨域飞行器惯导装置设计及抗冲击测量方法
16
作者 李存健 刘福朝 +2 位作者 刘宁 赵辉 周浩 《电子测量技术》 北大核心 2024年第5期167-172,共6页
跨域飞行器由于工作环境复杂多变,在飞行过程中运动参数受瞬态冲击影响较大,导致导航精度降低且难以稳定控制。针对瞬态冲击导致跨域飞行器难以获取准确运动参数的问题,本文研制了一种基于大小量程加速度计组合的惯性导航装置,并提出了... 跨域飞行器由于工作环境复杂多变,在飞行过程中运动参数受瞬态冲击影响较大,导致导航精度降低且难以稳定控制。针对瞬态冲击导致跨域飞行器难以获取准确运动参数的问题,本文研制了一种基于大小量程加速度计组合的惯性导航装置,并提出了一种大小量程加速度计切换策略,利用巴特沃斯滤波器对采集的数据进行滤波处理,通过预设阈值的累计和控制图算法和自主可变滑动窗口实现对冲击点的检测,并采用分段式线性插值方法保证了数据的同步性,最后通过模拟仿真和跌落台试验对本文所提出的切换策略进行试验验证,试验结果表明,分段式线性插值方法的估计误差不超过0.6 g,并在小量程加速计测量值饱和后,切换至大量程加速计的测量值,满足了实时切换的要求,进一步证明该惯性导航装置及大小量程切换策略可应用于飞行器进行跨域试验。 展开更多
关键词 跨域飞行器 惯性导航装置 累计和控制图法 分段式线性插值 跌落试验
下载PDF
圆截面组合桩加固滑坡的作用机理与合理嵌固深度物理模型试验研究
17
作者 宋成彬 李长冬 +3 位作者 王贵华 姚文敏 贺鑫 方堃 《安全与环境工程》 CAS CSCD 北大核心 2024年第1期135-149,共15页
目前在滑坡治理中,大截面人工挖孔桩因存在施工安全隐患大和效率低下等问题已在部分行业领域被限制使用,开展可机械化施工的圆截面组合桩研究已成为新的趋势,但当前对圆截面组合桩变形受力机理与合理嵌固深度的研究尚不够深入。基于自... 目前在滑坡治理中,大截面人工挖孔桩因存在施工安全隐患大和效率低下等问题已在部分行业领域被限制使用,开展可机械化施工的圆截面组合桩研究已成为新的趋势,但当前对圆截面组合桩变形受力机理与合理嵌固深度的研究尚不够深入。基于自主研发的圆截面组合桩加固滑坡物理模型试验系统,开展了不同工况下圆截面组合桩加固滑坡的物理模型试验,分析了滑体的变形演化过程,研究了圆截面组合桩加固下滑体与抗滑桩的变形受力特征,并对比分析了不同嵌固深度和桩顶连系梁对圆截面组合桩变形特征的影响,揭示了圆截面组合桩加固滑坡的作用机理。结果表明:①滑体的变形演化过程可分为压密、匀速变形、加速变形和变形破坏4个阶段;②前后桩均存在反弯点,反弯点会随着试验进程向桩顶移动,且后桩的反弯点更接近于滑动面;③当一排桩的嵌固深度保持不变、另一排桩的嵌固深度改变时,可将36%的桩长作为合理的嵌固深度;④连系梁使后桩的最大桩顶位移减小了15.6%,而对前桩的影响不大;⑤连系梁的存在降低了滑动面处的最大桩身弯矩,从而使得桩身弯矩分布更加合理。该研究成果有望为圆截面组合桩的设计提供借鉴和参考。 展开更多
关键词 滑坡加固 圆截面组合桩 加固机理 嵌固深度 物理模型试验
下载PDF
应用霍普金森压杆试验分析柠条动态力学特性
18
作者 李春东 张家宁 +1 位作者 曹丽英 张晓礼 《东北林业大学学报》 CAS CSCD 北大核心 2024年第5期102-106,共5页
为研究柠条的动态力学特性,采用分离式霍普金森压杆(SHPB)装置对柠条的横纹、顺纹试件进行动态压缩试验。通过改变驱动气压,使撞击杆分别以12、19、26 m·s^(-1)的初速度对入射杆撞击,比较不同应变率时,柠条试件的应力表现、破坏形... 为研究柠条的动态力学特性,采用分离式霍普金森压杆(SHPB)装置对柠条的横纹、顺纹试件进行动态压缩试验。通过改变驱动气压,使撞击杆分别以12、19、26 m·s^(-1)的初速度对入射杆撞击,比较不同应变率时,柠条试件的应力表现、破坏形态。结果表明:在相同的冲击能作用时,柠条顺纹试件的动态屈服应力强于横纹试件;随着应变率的提升,顺纹试件的动态屈服强度变化程度高于横纹试件,且应变率效应亦强于横纹试件。由动态应力-应变特性可知,柠条横纹试件经历弹性变形和弱强化两个阶段,顺纹试件经历弹性变形和压溃两个阶段。对柠条横纹试件动态屈服点后的应力-应变特性曲线,采用修正后的Johnson-Cook(J-C)本构模型进行拟合,获得良好的拟合度。 展开更多
关键词 柠条 霍普金森压杆试验 顺纹 横纹 动态力学特性
下载PDF
增生性瘢痕的影响因素分析及风险预测模型研究
19
作者 郝子佳 邢倩 +2 位作者 胡丹丹 剧宁 张洁 《组织工程与重建外科》 CAS 2024年第2期190-198,共9页
目的探究增生性瘢痕的影响因素并建立风险预测模型。方法选择2021年4月至2023年4月我院收治的102例增生性瘢痕患者作为增生性瘢痕组,102例伤口痊愈后未转化为增生性瘢痕的患者作为对照组。比较两组临床资料,采用随机森林算法筛选变量,... 目的探究增生性瘢痕的影响因素并建立风险预测模型。方法选择2021年4月至2023年4月我院收治的102例增生性瘢痕患者作为增生性瘢痕组,102例伤口痊愈后未转化为增生性瘢痕的患者作为对照组。比较两组临床资料,采用随机森林算法筛选变量,并通过多因素Logistic回归分析影响增生性瘢痕形成的因素;相关性E值法对研究结果的灵敏度进行分析;将多因素分析结果中的β值代入回归方程y=1-1(/1+e^(-z)),建立预测模型并评价其预测效能。结果随机森林算法筛选出9个变量,多因素Logistic回归分析结果显示,年龄≤30岁、瘢痕史、家族瘢痕史、创面愈合不良史、辛辣饮食习惯、伤口类型为烧伤、转化生长因子β1(TGF-β1)水平升高等,是导致增生性瘢痕形成的危险因素(P<0.05),采取瘢痕预防措施、肿瘤坏死因子α(TNF-α)水平升高为保护因素(P<0.05);E=1.984,95%CI下限为1.216,研究结果的灵敏度较高;当模型预测增生性瘢痕形成概率为0.85时,约登指数最高(74.38),预测效果最好,预测准确度、灵敏度和特异度分别为89.03%、85.73%、88.65%。预测模型的ROC曲线下面积为0.847(95%CI:0.782~0.913,P<0.001),区分度较好;十字交叉试验结果显示,训练集和验证集模型参数的拟合度较高(Nagelkerke R2=0.602),模型较稳定。结论年龄、瘢痕史、饮食习惯、血清炎症因子水平等与增生性瘢痕的形成有关,临床上应采取个性化干预措施,以降低增生性瘢痕形成率。 展开更多
关键词 增生性瘢痕 影响因素 预测模型 十字交叉试验
下载PDF
考虑截面规则性的柱状节理岩体变形及强度特性研究
20
作者 朱姝 阙相成 +1 位作者 朱珍德 朱其志 《岩土力学》 EI CAS CSCD 北大核心 2024年第1期213-225,共13页
柱状节理岩体的复杂结构使其现场力学参数的确定存在困难,可靠地估计柱状节理岩体强度及变形特性对工程安全至关重要。结合Voronoi图形及3D打印技术制作不规则柱状节理岩体光敏树脂模具,并制备了具有不同倾角的规则及不规则柱状节理岩... 柱状节理岩体的复杂结构使其现场力学参数的确定存在困难,可靠地估计柱状节理岩体强度及变形特性对工程安全至关重要。结合Voronoi图形及3D打印技术制作不规则柱状节理岩体光敏树脂模具,并制备了具有不同倾角的规则及不规则柱状节理岩体试样。基于开展的单轴压缩试验结果,分析不同截面柱状节理岩体的变形及强度特性差异。根据试样最终破坏形态,揭示柱状节理岩体破坏模式及机制。结合已有研究结果,描述节理面材料对柱状节理岩体破坏形态及强度的影响。基于传统节理系数方法,提出了更能反映柱状节理岩体柱体结构特征的修正节理系数方法。采用修正节理系数法建立规则及不规则柱状节理岩体试验结果与现场变形及强度参数间的经验关系,将所提出计算公式应用于白鹤滩水电站工程,预测结果与现场实测值及RMR法(RMR为岩石质量评分指标)、Q法(Q为岩体质量指标)的预测值进行比较。结果表明,对于现场变形和强度参数,所提出的修正节理系数法的预测结果与现场实测结果较为吻合。 展开更多
关键词 截面规则性 柱状节理岩体 变形及强度特性 物理模型试验 经验关系
下载PDF
上一页 1 2 87 下一页 到第
使用帮助 返回顶部