期刊文献+
共找到7,150篇文章
< 1 2 250 >
每页显示 20 50 100
广义Mycielski图的补图的若干参数 预览
1
作者 刘志霞 边红 +1 位作者 刘敏 于海征 《厦门大学学报:自然科学版》 CAS CSCD 北大核心 2019年第2期288-291,共4页
为了寻找一类具有任意大色数但不含三角形的图类,Mycielski提出了一种有趣的图变换,称之为图G的Mycielskian图,记为μ(G).Lam等对μ(G)的定义做了一个自然的推广,提出了广义Mycielskian图(也被Tardif称为conesover图),记为μm(G),其中m... 为了寻找一类具有任意大色数但不含三角形的图类,Mycielski提出了一种有趣的图变换,称之为图G的Mycielskian图,记为μ(G).Lam等对μ(G)的定义做了一个自然的推广,提出了广义Mycielskian图(也被Tardif称为conesover图),记为μm(G),其中m代表正整数.本文中给出了广义Mycielskian图的补图的控制数、全控制数、packing数和openpacking数的明确结果. 展开更多
关键词 广义Mycielskian图 补图 控制数 packing
在线阅读 免费下载
功能性鼻内镜鼻窦手术后总鼻道填塞与不填塞的比较观察 预览
2
作者 张佳凤 金晓杰 +5 位作者 何平 周川 赵辉 施薇薇 郝亚琳 董琼娜 《中国中西医结合耳鼻咽喉科杂志》 2019年第1期45-48,共4页
目的探讨功能性内镜鼻窦手术(FESS)后总鼻道不填塞的安全性和患者体验感。方法138例患者分成两组,一组为总鼻道不填塞组(A组)85例,另一组为填塞组(B组)53例,比较两组术后的临床症状、并发症及患者体验感(VAS评分)。结果A组在安全性方面... 目的探讨功能性内镜鼻窦手术(FESS)后总鼻道不填塞的安全性和患者体验感。方法138例患者分成两组,一组为总鼻道不填塞组(A组)85例,另一组为填塞组(B组)53例,比较两组术后的临床症状、并发症及患者体验感(VAS评分)。结果A组在安全性方面和B组无明显差异,而在患者体验感方面明显优于B组,两组评分差异有统计学意义(P<0.05)。两组在6个月的随访期内均无明显术腔粘连发生。结论通过术前患者病情轻重程度评估,术中恰当的处理,大多数FESS术后患者可不进行总鼻道填塞,这可明显减轻患者的术后痛苦,节省医疗资源,值得推广应用。 展开更多
关键词 功能性鼻内镜鼻窦手术 总鼻道 填塞
在线阅读 下载PDF
填料上塔的设计浅析 被引量:1
3
作者 张苏宁 杨文娟 +2 位作者 张申 陈茹茹 王永胜 《中国化工装备》 CAS 2019年第2期40-44,共5页
详细地介绍了填料上塔用于空分装置中的优势,填料的各种类型及特性,内件的各个组成及作用,填料上塔结构的优化.
关键词 填料 内件 结构优化
Effective enhancement of the emission efficiency of tetraphenylporphyrin in solid state by tetraphenylethene modification
4
作者 Nan Jiang Yijia Wang +2 位作者 Anjun Qin Jing Zhi Sun Ben Zhong Tang 《中国化学快报:英文版》 SCIE CAS CSCD 2019年第1期143-148,共6页
Tetraphenylporphyrin(TPP)is a typical red-emitting luminogen showing evident aggregation caused quenching(ACQ)effect.To enhance its emission efficiency in solid state,four tetraphenylethene(TPE)units were attached to ... Tetraphenylporphyrin(TPP)is a typical red-emitting luminogen showing evident aggregation caused quenching(ACQ)effect.To enhance its emission efficiency in solid state,four tetraphenylethene(TPE)units were attached to the four meso-positions of TPP core via ester group through a facile and efficient route.The derived compound(4(TPE-COO)-TPP)emits red fluorescence(peak at 655 nm)with a good quantum efficiency(F)of 7.5%,which is much higher than that of TPP(Φ~0.1%).In molecular aggregate formed in tetrahydrofuran(THF)and water mixtures,4(TPE-COO)-TPP has a relative high F of 12%.The evidently subdued ACQ behavior can be ascribed to the propeller shape and bulky size of the TPE units,which prevent the close packing and strong p-p interaction of TPP cores.The loose molecular packing and weak interchromophore interactions were validated by different characterization methods including UV-visible absorption,steady state and transient fluorescence spectroscope,X-ray diffraction and scanning electronic microscope observations.It is noted that 4(TPE-COO)-TPP has an emission efficiency of 14.4%in dilute THF solution.This is due to the conjugation break between the TPP and TPE moieties,the rotational and vibrational motions of the phenyl groups cannot quench the fluorescence of 4(TPE-COO)-TPP. 展开更多
关键词 Aggregation-induced EMISSION Tetraphenylethene PORPHYRIN Red EMISSION Molecular packing
Communication Resource Planning Algorithm Based on Time Triggered DIMA Architecture 预览
5
作者 Hongchun Wang Buqun Luan Wensheng Niu 《北京理工大学学报:英文版》 EI CAS 2019年第2期327-335,共9页
Traditional scheduling algorithms for avionics communication have the shortcoming of messages accumulation,the efficiency and reliability of the service can be improved by combining the distributed integrated modular ... Traditional scheduling algorithms for avionics communication have the shortcoming of messages accumulation,the efficiency and reliability of the service can be improved by combining the distributed integrated modular avionics(DIMA)system with a time trigger mechanism.To further improve the utilization of system resources,the static scheduling algorithm of time triggered service is studied.By making the time trigger message schedule dispersedly,the stabilities of both the available time slots for the event triggered messages and the system will be improved.An improved two-dimensional bin packing algorithm is also presented to achieve the above-mentioned purpose with an extra benefit of better delay performance. 展开更多
关键词 distributed integrated MODULAR AVIONICS TIME-TRIGGERED TWO-DIMENSIONAL BIN packing ALGORITHM
在线阅读 免费下载
基于格的身份基矩阵加密方案 预览
6
作者 李明祥 王洪涛 《信息网络安全》 CSCD 北大核心 2019年第1期34-41,共8页
基于格的密码体制是一类抗量子计算攻击的公钥密码体制。量子计算机一旦问世,将对目前广泛使用的公钥密码体制,如基于大数分解的密码体制、基于离散对数的密码体制等,造成冲击。因此基于格的密码体制近年来成为网络安全领域的研究热点... 基于格的密码体制是一类抗量子计算攻击的公钥密码体制。量子计算机一旦问世,将对目前广泛使用的公钥密码体制,如基于大数分解的密码体制、基于离散对数的密码体制等,造成冲击。因此基于格的密码体制近年来成为网络安全领域的研究热点。身份基加密体制简化了用户公钥的管理过程,它可应用到资源受限的环境中。目前人们已提出了许多基于格的身份基加密方案,但这些方案都是单比特加密方案。鉴于此,文章利用Peikert、Vaikuntanathan和Waters的密文包装技术,设计了一个基于格的姐阵公钥加密方案,并基于LWE问题困难假设,证明了该公钥加密方案是IND-CPA安全的。文章进而以所提出的公钥加密方案为基础,依据Gentry、Peikert和Vaikuntanathan提出的对偶加密系统,构造了一个基于格的身份基矩阵加密方案,并基于LWE问题困难假设,证明了该身份基加密方案满足IND-sID-CPA安全。 展开更多
关键词 身份基加密 LWE问题 包装
在线阅读 下载PDF
填料类型对MBBR启动及运行效能的影响 预览
7
作者 刘辉 《科技创新与应用》 2019年第21期69-70,75共3页
通过实验的方式,对两种不同的填料的废水处理能力进行研究。将A、B两种填料分别放入两个不同的生物膜反应器(MBBR)中,并对其处理能力进行观察,包括水质、形貌、特征等等方面。经过一系列的试验证明,A填料的各方面性能要优于B填料,更适... 通过实验的方式,对两种不同的填料的废水处理能力进行研究。将A、B两种填料分别放入两个不同的生物膜反应器(MBBR)中,并对其处理能力进行观察,包括水质、形貌、特征等等方面。经过一系列的试验证明,A填料的各方面性能要优于B填料,更适用于生物膜反应器。 展开更多
关键词 移动床生物膜反应器 填料 废水处理 起动 运行效能
在线阅读 下载PDF
An Overview of Molecular Packing Mode in Two-Dimensional Organic Nanomaterials via Supramolecular Assembly
8
作者 Ling-Zhi Jin Sha-Sha Wang +1 位作者 Ling-Hai Xie Wei Huang 《中国化学:英文版》 SCIE CAS CSCD 2019年第4期405-416,共12页
Two-dimensional(2D)organic nanomaterials are attracting increasing research interest and expected to be the ideal candidate for futureproofed flexible electronics and biotechnologies.Owing to the complex molecular str... Two-dimensional(2D)organic nanomaterials are attracting increasing research interest and expected to be the ideal candidate for futureproofed flexible electronics and biotechnologies.Owing to the complex molecular structures and multiple intermolecular interactions in organic systems,deeper understanding of rational molecular design and assembly principles is urgently required.In this review,a collection of molecular packing mode in the 2D organic nanomaterials via supramolecular assembly is presented,so as to help explicit the relationship among molecular structures,supramolecular interactions and molecular packing motifs in 2D assembly systems.We also provide a rational and accessible schematic model to demonstrate several typical kinds of molecular packing motifs for the prediction of the 2D morphology. 展开更多
关键词 Molecular PACKING Mode TWO-DIMENSIONAL ORGANIC NANOMATERIALS SUPRAMOLECULAR Assembly
Influence of wall friction on granular column
9
作者 杨阳阳 张晟 +3 位作者 林平 万江锋 杨磊 丁淑蓉 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第1期639-644,共6页
Granular packings under gravity in frictional and frictionless silos were simulated and the influence of the wall friction on the normal force distribution was investigated. Although there is an obvious Janssen effect... Granular packings under gravity in frictional and frictionless silos were simulated and the influence of the wall friction on the normal force distribution was investigated. Although there is an obvious Janssen effect in frictional silos, only a slight influence on the geometry of packing was found. The law of normal force distribution is different for frictional and frictionless walls, which is related to the pressure profile. A modified formula with consideration of the pressure profile was well fitted to the simulation results. 展开更多
关键词 Janssen effect force distribution WALL FRICTION PACKING CONFIGURATION
Mass transfer area in a multi-stage high-speed disperser with split packing
10
作者 Tao Ai Aslam M.Mudassar +1 位作者 Ziqi Cai Zhengming Gao 《中国化学工程学报:英文版》 SCIE EI CAS CSCD 2019年第4期772-780,共9页
In this study, the mean droplet diameter in the cavity zone and the total mass transfer area of a multi-stage highspeed disperser(HSD) reactor with different packing combinations were measured and evaluated. The effec... In this study, the mean droplet diameter in the cavity zone and the total mass transfer area of a multi-stage highspeed disperser(HSD) reactor with different packing combinations were measured and evaluated. The effects of rotational speed and packing radius, as well as the packing ring radius and numbers, on the mean droplet diameter and the total mass transfer area were evaluated. A model was established to calculate the mass transfer area in the cavity zone in the HSD reactor, and it was found that the packings contribute 61%–82% of the total mass transfer area. A correlation for predicting the mass transfer area in the packing zone was regressed by the dimensionless analysis method. An enhancement factor based on the mass transfer area in the packing zone was proposed to evaluate the effect of packing combination on mass transfer area. Two optimum packing combinations were proposed in consideration of the mean droplet diameter and the enhancement factor. 展开更多
关键词 HIGH-SPEED DISPERSER Mean droplet diameter Mass transfer area SPLIT PACKING
大庆石化裂解二套装置急冷油塔检修前后运行浅析 预览
11
作者 彭海波 《江西化工》 2019年第1期158-162,共5页
简述了裂解二套装置急冷油塔的工艺流程;针对2018年检修前后急冷油塔运行状态,包括压差、顶釜温、循环量等进行对比,并分析了主要影响因素;并对今后的运行提出合理化建议。
关键词 急冷油 压差 填料 化学清洗
在线阅读 免费下载
电商物流包装贮运对‘翡脆’荔枝贮藏品质的影响 预览
12
作者 蒋侬辉 黄泽鹏 +3 位作者 刘伟 凡超 金峰 向旭 《食品工业科技》 CAS 北大核心 2019年第18期249-254,共6页
本文以荔枝新品种‘翡脆’、传统大宗品种‘桂味’为试材,分析了运用冰袋结合电商包装的物流包装贮运方法下荔枝果实采后生理及贮藏品质变化,同时也探究了‘翡脆’品种的贮藏特性。结果表明,电商物流包装贮运方式显著(P<0.05)降低了... 本文以荔枝新品种‘翡脆’、传统大宗品种‘桂味’为试材,分析了运用冰袋结合电商包装的物流包装贮运方法下荔枝果实采后生理及贮藏品质变化,同时也探究了‘翡脆’品种的贮藏特性。结果表明,电商物流包装贮运方式显著(P<0.05)降低了荔枝果实的呼吸强度、相对电导率;减缓了荔枝可溶性固形物(TSS)、可滴定酸(TA)及VC含量的下降,并抑制了ΔE*值的上升和L*值的下降,保持了较好的果实感官品质。电商物流包装贮运方式还显著(P<0.05)降低了贮运期间特别是贮运中后期荔枝的失重率、褐变指数,并维持了较高的好果率,因此电商物流包装贮运方式可延缓果实衰老,延长贮藏期。同时,与‘桂味’相比,荔枝新品种‘翡脆’显示出更低的呼吸强度、相对电导率、ΔE*值及感官品质变化。此外,‘翡脆’荔枝的失重率、褐变指数低于‘桂味’,好果率及贮藏期均高于‘桂味’,表明‘翡脆’荔枝有着较好的持水性和耐贮性。 展开更多
关键词 电商物流 '翡脆’荔枝 贮运 包装 采后生理 品质
在线阅读 免费下载
传统食品企业品牌包装再设计之研究——以天津长城牌食品为例 预览
13
作者 牛津 《现代食品》 2019年第7期51-54,共4页
随着中国经济的飞速发展,食品行业也在不断发展,面对消费不断升级的市场,消费者对食品也有着更高的期待,也更注重食品商品的包装,毕竟在消费购买过程当中包装美观也是引起当下消费者的一个重要原因。本文以天津进出口食品集团的天津传... 随着中国经济的飞速发展,食品行业也在不断发展,面对消费不断升级的市场,消费者对食品也有着更高的期待,也更注重食品商品的包装,毕竟在消费购买过程当中包装美观也是引起当下消费者的一个重要原因。本文以天津进出口食品集团的天津传统食品企业长城牌食品为例,深度分析了其新的包装设计的思考与过程,及其设计给品牌在消费市场上带来的新活力。 展开更多
关键词 食品行业 出口食品 包装 品牌销售战略 长城牌
在线阅读 下载PDF
Evaluation of Inocula and Packing Material for Acceleration of Start-Up in Biofilters 预览
14
作者 Li Chao Zhao Dongfeng +3 位作者 Mu Guiqin Song Xiangning Zhang Tingting Liu Jun 《中国炼油与石油化工:英文版》 SCIE CAS 2019年第2期67-75,共9页
Several strategies with different combination of inocula and packing material were investigated to obtain the optimal start-up time and elimination capacity (EC) in toluene biofiltration. The inocula contained the act... Several strategies with different combination of inocula and packing material were investigated to obtain the optimal start-up time and elimination capacity (EC) in toluene biofiltration. The inocula contained the activated sludge and toluene degrading bacteria, and the packing material consisted of different mixing ratios of peat and wood chips. A final toluene load of 21.2 g/(m3·h) was attained step by step in four parallel biofilters. A shortest start-up time of 15 days and a highest EC of 17.0 g/(m3·h) were observed in the biofilter B-4, which was inoculated with a special microbial consortium consisting of three strains of toluene degrading bacteria and was packed with the mixture of peat and wood chips at a ratio of 80:20 (w/w). These results indicated that inoculating pre-acclimatized microbes dramatically shortened the start-up time, and such a composition of packing material could maintain an appropriate environment (with the bed porosity and water content equating to 0.45 and 1.96, respectively) for the growth of dominant toluene degrading bacteria in the biofilter. 展开更多
关键词 ACCELERATION of START-UP BIOFILTER INOCULA PACKING material
在线阅读 下载PDF
Design of packing cup interference fit value of hypercompressors for low density polyethylene production
15
作者 Da LEI Xuehong LI +1 位作者 Yun LI Xiwen REN 《能源前沿:英文版》 CSCD 2019年第1期107-113,共7页
The hypercompressor is one of the core facilities in low density polyethylene production,with a discharge pressure of approximately 300 MPa.A packing cup is the basic unit of cylinder packing,assembled by the interfer... The hypercompressor is one of the core facilities in low density polyethylene production,with a discharge pressure of approximately 300 MPa.A packing cup is the basic unit of cylinder packing,assembled by the interference fit between an inner cup and an outer cup.Because the shrink-fitting prestresses the packing cup,serious design is needed to gain a favorable stress state,for example,a tri-axial compressive stress state.The traditional method of designing the interference fit value for packing cups depends on the shrink-fit theory for thickwalled cylinder subject to internal and external pressure.According to the traditional method,critical points are at the inner radii of the inner and external cup.In this study,the finite element method(FEM)has been implementcd to determine a more accurate stress level of packing cups.Different critical points have been found at the edge of lapped sealing surfaces between two adjacent packing cups.The maximum Von Mises equivalent stress in a packing cup increases after a decline with the rise of the interference fit value.The maximum equivalent stress initially occurs at the bore of the inner cup,then at the edge of lapped mating surfaces,and finally at the bore of the outer cup,as the interference radius increases.The traditional method neglects the influence of axial preloading on the interference mating pressure.As a result,it predicts a lower equivalent stress at the bore of the external cup.A higher interference fit value accepted by the traditional method may not be feasible as it might already make packing cups yield at the edge of mating surfaces or the bore of the external cup.Along with fatigue analysis,the feasible range of interference fit value has been modified by utilizing FEM.The modified range tends to be narrower and safer than the one derived from the traditional method,after getting rid of shrink-fit values that could result in yielding in a real packing cup. 展开更多
关键词 INTERFERENCE FIT VALUE PACKING CUP hypercompressor finite element method(FEM)
Dimension Results for Space-anisotropic Gaussian Random Fields
16
作者 Wen Qing NI Zhen Long CHEN Wei Gang WANG 《数学学报:英文版》 SCIE CSCD 2019年第3期391-406,共16页
Let X = {X(t) ∈ R^d, t ∈ R^N} be a centered space-anisotropic Gaussian random field whose components satisfy some mild conditions. By introducing a new anisotropic metric in R^d, we obtain the Hausdorff and packing ... Let X = {X(t) ∈ R^d, t ∈ R^N} be a centered space-anisotropic Gaussian random field whose components satisfy some mild conditions. By introducing a new anisotropic metric in R^d, we obtain the Hausdorff and packing dimension in the new metric for the image of X. Moreover, the Hausdorff dimension in the new metric for the image of X has a uniform version. 展开更多
关键词 HAUSDORFF DIMENSION packing DIMENSION GAUSSIAN RANDOM field UNIFORM DIMENSION
发芽糙米中粗多糖的纯化及分子量测定 预览
17
作者 刘晓飞 张宇 +4 位作者 王薇 关桦楠 张娜 马永强 卢淑雯 《食品工业科技》 CAS 北大核心 2019年第2期19-24,共6页
本文对发芽糙米粗多糖进行纯化,通过比较活性炭吸附法、过氧化氢氧化法、大孔树脂吸附法三种方法的脱色效果,以及Sevage法、三氯乙酸法、酶与Sevage结合方法三种方法的脱蛋白效果,筛选出发芽糙米粗多糖脱色、脱蛋白的最佳方法。分别比较... 本文对发芽糙米粗多糖进行纯化,通过比较活性炭吸附法、过氧化氢氧化法、大孔树脂吸附法三种方法的脱色效果,以及Sevage法、三氯乙酸法、酶与Sevage结合方法三种方法的脱蛋白效果,筛选出发芽糙米粗多糖脱色、脱蛋白的最佳方法。分别比较了DEAE-Sepharose CL-6B、DEAE Fast Flow、DEAE Sepharose 52三种柱层析填料对糙米粗多糖的层析纯化效果,筛选出最优填料。并对纯化后的发芽糙米多糖各组分进行分子量的测定。结果表明:大孔树脂AB-8对发芽糙米粗多糖脱色效果最佳,脱色率为86.57%,多糖损失率为28.96%。酶-Sevage法脱蛋白效果较好,且多糖损失率低,脱蛋白率为74.36%,多糖损失率为14.09%。对发芽糙米多糖进行柱层析的最佳填料为DEAE-Sepharose CL-6B。根据线性回归方程计算其平均分子量,水洗多糖组分的平均分子量为1.47×10~5Da,盐洗多糖组分的平均分子量分别为9.62×10~5、5.59×10~6、3.15×10~5Da。结论:确定了针对发芽糙米粗多糖的去除蛋白质和脱色的方法,并筛选出最佳的柱层析填料,分离出四个组分发芽糙米多糖,为发芽糙米粗多糖的提取、纯化、分离逐渐转变为工业化生产提供了理论基础。 展开更多
关键词 发芽糙米 粗多糖 纯化 柱层析 填料 平均分子量
在线阅读 免费下载
Effect of concentration and adsorption time on the formation of a large-scale origami pattern 预览
18
作者 Wen-Jing Liu Ping Zhang +5 位作者 Tong Sun Lin Li Yu-Hui Wei Kai-Zhe Wang Lin Liu Bin Li 《核技术:英文版》 SCIE CAS CSCD 2019年第7期62-67,共6页
The arrangement of DNA-based nanostructures into the desired large-scale periodic pattern with the highest possible accuracy and control is essential for the DNA application in functional biomaterials;however, formati... The arrangement of DNA-based nanostructures into the desired large-scale periodic pattern with the highest possible accuracy and control is essential for the DNA application in functional biomaterials;however, formation of a DNA nanostructure pattern without utilizing the molecular interactions in nanotechnology field remains difficult. In this article, we use the optimal concentration and adsorption time of origami to induce DNA origami in the form of a large-scale 2D pattern on mica without changing the origami itself. DNA origami structures can form a pattern by close packing of symmetric and electrostatic interactions between ions, which was confirmed by the atomic force microscopy images. Furthermore, we identified favorable conditions for the concentration of enable pattern formation with DNA origami. This work provides an insight to understand the adsorption of DNA on mica and guides researches on regular DNA nanostructure pattern, which can serve as templates for pattern formation of proteins or other biomolecules. 展开更多
关键词 DNA ORIGAMI PATTERN ATOMIC force MICROSCOPY CLOSE packing
在线阅读 下载PDF
Impact of alkyl chain branching positions on molecular packing and electron transport of dimeric perylenediimide derivatives 预览
19
作者 Yuan Guo Guangchao Han Yuanping Yi 《能源化学:英文版》 SCIE EI CAS CSCD 2019年第8期138-143,I0006共7页
Side chains play a critical role in tuning intermolecular interaction and charge transport in organic semiconductors. Here, we have systematically investigated the impact of branching positions of the alkyl side chain... Side chains play a critical role in tuning intermolecular interaction and charge transport in organic semiconductors. Here, we have systematically investigated the impact of branching positions of the alkyl side chains on the molecular packing and electron transport properties of a series of bay-linked dimeric perylenediimide(PDI) derivatives by atomistic molecular dynamics simulations in combination with charge transfer rate theory and kinetic Monte Carlo simulations. The results show that despite of different branching positions of the alkyl chains,π–π stacking is effectively inhibited for all the dimeric PDI derivatives. As the branching position moves away from the PDI backbone, the appearance of the alkyl atoms around the PDI backbone will first decrease and then increase. Correspondingly, the short contacts between the PDI moieties are first enhanced and then reduced. In particular, when the branching position is at the third carbon atom, the intermolecular connectivity becomes the most effective and the electron mobility is significantly increased by 2 times. 展开更多
关键词 Molecular packing Electron MOBILITY Branching POSITION PERYLENEDIIMIDE
在线阅读 下载PDF
大型自然通风逆流式冷却塔改造实践及经济性分析 预览
20
作者 潘雷鸣 《电力系统装备》 2019年第14期179-180,共2页
本文针对浙能集团某600MW超临界火力发电厂冷却塔塔芯材料进行研究,通过方案比选提出了冷却塔改造的技术路线,并最终确认最佳方案。项目实施后通过性能测试,计算了改造的节能量和经济性。
关键词 冷却塔 填料 片距 出塔水温 节能 效率
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈