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Crack detection for wading-concrete structures using water irrigation and electric heating

《结构与土木工程前沿(英文)》 2023年 第17卷 第3期   页码 368-377 doi: 10.1007/s11709-022-0926-x

摘要: Cracking in wading-concrete structures has a worse impact on structural safety compared with conventional concrete structures. The accurate and timely monitoring of crack development plays a significant role in the safety of wading-concrete engineering. The heat-transfer rate near a crack is related to the flow velocity of the fluid in the crack. Based on this, a novel crack-identification method for underwater concrete structures is presented. This method uses water irrigation to generate seepage at the interface of a crack; then, the heat-dissipation rate in the crack area will increase because of the convective heat-transfer effect near the crack. Crack information can be identified by monitoring the cooling law and leakage flow near cracks. The proposed mobile crack-monitoring system consists of a heating system, temperature-measurement system, and irrigation system. A series of tests was conducted on a reinforced-concrete beam using this system. The crack-discrimination index ψ was defined, according to the subsection characteristics of the heat-source cooling curve. The effects of the crack width, leakage flow, and relative positions of the heat source and crack on ψ were studied. The results showed that the distribution characteristics of ψ along the monitoring line could accurately locate the crack, but not quantify the crack width. However, the leakage flow is sensitive to the crack width and can be used to identify it.

关键词: structural health monitoring     underwater concrete structure     fiber Bragg grating     crack detection     temperature tracer method    

Optimizing the configuration of a clearwell by integrating pilot and full-scale tracer testing

LIU Wenjun, DU Zhipeng, JIN Junwei

《环境科学与工程前沿(英文)》 2007年 第1卷 第3期   页码 270-275 doi: 10.1007/s11783-007-0045-x

摘要: In this paper, the main factors impacting the plug flow pattern of a clearwell were investigated by integrating pilot-scale, full-scale clearwell tracer testing and computational fluid dynamics (CFD) simulation. It was found that pilot tracer testing, full-scale tracer testing and CFD simulation all demonstrated that the correlation between the ratio of / and can be approximately expressed by: / = 0.189 4ln()-0.049 4. This study confirmed that the installation of baffles within clearwells is an efficient way to optimize their configuration. In addition, the inlet velocity has a minimal contribution to the ratio of /. However, the ratio of turning channel width to channel width () significantly contributes to the ratio of/. The optimal ratio of is 0.8–1.2 for maintaining better plug flow pattern. The number of turning channels is one of the main factors that impact the ratio of /. When increasing the number of turning channels, a lower ratio of / is obtained.

Real-time tool condition monitoring method based on temperature measurement and artificial neural network

《机械工程前沿(英文)》 doi: 10.1007/s11465-021-0661-3

摘要: Tool failures in machining processes often cause severe damages of workpieces and lead to large quantities of loss, making tool condition monitoring an important, urgent issue. However, problems such as practicability still remain in actual machining. Here, a real-time tool condition monitoring method integrated in an in situ fiber optic temperature measuring apparatus is proposed. A thermal simulation is conducted to investigate how the fluctuating cutting heats affect the measuring temperatures, and an intermittent cutting experiment is carried out, verifying that the apparatus can capture the rapid but slight temperature undulations. Fourier transform is carried out. The spectrum features are then selected and input into the artificial neural network for classification, and a caution is given if the tool is worn. A learning rate adaption algorithm is introduced, greatly reducing the dependence on initial parameters, making training convenient and flexible. The accuracy stays 90% and higher in variable argument processes. Furthermore, an application program with a graphical user interface is constructed to present real-time results, confirming the practicality.

关键词: tool condition monitoring     cutting temperature     neural network     learning rate adaption    

彩色测温方法中物体辐射色域的界定和划分

王安全,程晓舫,陆少松

《中国工程科学》 2002年 第4卷 第8期   页码 54-57

摘要:

介绍了彩色测温方法的基本原理,并基于可见光波段内光谱发射率的线性模型给出物体辐射颜色色品的表述;明确了一个色品最多只能求解出两个温度;解决了彩色测温方法中物体辐射色域的界定问题,并将辐射色域划分为温度单解域和双解域。

关键词: 辐射测温     彩色测温     色域     发射率    

Performance of a bi-layer solar steam generation system working at a high-temperature of top surface

Jinxin ZHONG, Congliang HUANG

《能源前沿(英文)》 2023年 第17卷 第1期   页码 141-148 doi: 10.1007/s11708-021-0725-4

摘要: Many efforts have been focused on enhancing the vapor generation in bi-layer solar steam generation systems for obtaining as much pure water as possible. However, the methods to enhance the vapor temperature is seldom studied although the high-temperature vapor has a wide use in medical sterilization and electricity generation. In this work, to probe the high-temperature vapor system, an improved macroscopic heat and mass transfer model was proposed. Then, using the finite element method to solve the model, the influences of some main factors on the evaporation efficiency and vapor temperature were discussed, including effects of the vapor transport conditions and the heat dissipation conditions. The results show that the high-temperature vapor could not be obtained by enhancing the heat-insulating property of the bi-layer systems but by applying the optimal porosity and proper absorbers. This paper is expected to provide some information for designing a bi-layered system to produce high-temperature vapor.

关键词: solar steam generation     solar energy     numerical method     porous material    

Room temperature preparation of hydrazine-linked covalent organic frameworks coated capillaries for

《化学科学与工程前沿(英文)》 2023年 第17卷 第5期   页码 548-556 doi: 10.1007/s11705-022-2252-1

摘要: Covalent organic frameworks (COFs) have been increasingly used in capillary electrochromatography due to their excellent characteristics. In this work, hydrazine-linked TFPB-DHzDS (TFPB: 1,3,5-tris(4-formylphenyl)benzene; DHzDS: 2,5-bis(3-(ethylthio)propoxy)terephthalohydrazide) was first synthesized by a simpler and easier method at room temperature and introduced into capillary electrochromatography as coating material. The TFPB-DHzDS coated capillaries were prepared by an in-situ growth process at room temperature. After optimizing the coating concentration and experimental conditions of capillary electrochromatography, baseline separation of two groups of polycyclic aromatic hydrocarbons was achieved based on the TFPB-DHzDS coated capillary. And the established method was used successfully to determine PAHs in natural water and soil samples. The spiked recoveries of polycyclic aromatic hydrocarbons in these samples ranged from 90.01% to 111.0%, indicating that the method is reliable and could detect polycyclic aromatic hydrocarbons in natural samples. Finally, molecular simulation was applied to study and visualize the interaction between the analytes and coating COF materials to investigate the molecular level separation mechanism further.

关键词: hydrazine-linked TFPB-DHzDS     in-situ growth method     open-tubular capillary electrochromatography     molecular simulations    

An optimized solar-air degree-day method to evaluate energy demand for poultry buildings in different

Yang WANG, Baoming LI

《农业科学与工程前沿(英文)》 2020年 第7卷 第4期   页码 478-489 doi: 10.15302/J-FASE-2019289

摘要:

The degree-day method is widely used to determine energy consumption but cannot be directly applied to poultry buildings without improvements in its accuracy. This study was designed to optimize the degree-day calculation and proposes a solar-air degree-day method, which can be used to calculate the cooling and heating degree-days and the annual cooling and heating loads under different climate conditions for poultry buildings. In this paper, the solar-air degree-day method was proposed, which considers the effects of solar radiation with different wall orientations and surface colors. Five Chinese cities, Harbin, Beijing, Chongqing, Kunming and Guangzhou, were selected to represent different climate zones to determine the solar-air degree-days. The heating and cooling energy requirements for different climates were compared by DeST (Designer’s Simulation Toolkit) simulation and the solar-air degree-day method. Approaches to decrease energy consumption were developed. The results showed that the maximum relative error was less than 10%, and the new method was not significantly different from the DeST simulation ( >0.05). The accuracy of calculating energy requirements was improved by the solar-air degree-day method in the different climate zones. Orientation and surface color effects on energy consumption need to be considered, and external walls of different orientations should have different surface colors.

关键词: base temperature     energy consumption     solar radiation     orientation     surface color    

利用六氟化硫示踪技术预估不同年龄阶段的放牧荷斯坦奶牛甲烷排放量

Steven J. Morrison, Judith McBride, Alan W. Gordon, Alastair R. G. Wylie, 闫天海

《工程(英文)》 2017年 第3卷 第5期   页码 753-759 doi: 10.1016/J.ENG.2017.03.018

摘要:

动物和日粮因素对牛肠道甲烷排放量影响的相关研究已经很普遍,但是关于放牧青年奶牛的甲烷排放量的可参考数据较少。本研究评估了荷斯坦奶牛在多年生黑麦草草地放牧时的生理状态对甲烷排放量的影响,分别进行了以下两个试验:试验1从2011年5月开始,为期11个星期,试验2从2011年8月开始,为期10个星期。在每个试验中,将荷斯坦奶牛分成三个处理组(每组12头),分别由小牛犊、一岁的母牛犊和妊娠母牛组成(平均年龄分别为8.5、14.5和20.5月龄)。在每个试验的最后一个星期利用六氟化硫示踪技术预估每头牛的甲烷排放量。干物质摄入量由代谢能需要量除以牧草中的代谢能含量计算而得。正如预期一样,活体重随年龄的增加而增加(P < 0.001),然而试验1中三个分组的体增重没有差异,试验2中的体增重随着年龄增加有不同程度的减少(P < 0.001)。在试验1中,妊娠母牛高于小牛犊的甲烷排放量(P < 0.001),而一岁母牛犊的甲烷排放量最高(g•d-1)。当用单位活体重、干物质摄入量和总能摄入量表示甲烷排放量时,一岁母牛犊比小牛犊和妊娠母牛的排放速率更高(P < 0.001)。在试验2中,甲烷排放量(g•d-1)随着年龄增加呈线性上升(P < 0.001),但是这种差异在一岁母牛犊和妊娠母牛中并不显著。妊娠母牛的甲烷/活体重的比值低于另外两组(P < 0.001),小牛犊的总能摄入量中甲烷能量输出的比值低于一岁母牛犊和妊娠母牛(P < 0.05)。根据所有数据建立甲烷排放量的预测方程。所有关系均为显著(P < 0.001),R²值的分布范围为0.630~0.682。这些模型表明:每增加1 kg活体重,甲烷排放量增加0.252 g•d-1;每增加1 kg•d-1干物质摄入量,甲烷排放量增加14.9 g•d-1;每增加1 MJ•d-1总能摄入量,甲烷能量输出增加0.046 MJ•d-1。当实际甲烷排放量不可测时,这些结果为我们提供了预估放牧母牛甲烷排放量的另一种方法。

关键词: 甲烷排放量     放牧奶牛     预测     六氟化硫示踪技术    

A nano-scale alignment method for imprint lithography

WANG Li, LU Bing-heng, DING Yu-cheng, QIU Zhi-hui, LIU Hong-zhong

《机械工程前沿(英文)》 2006年 第1卷 第2期   页码 157-161 doi: 10.1007/s11465-006-0014-2

摘要: A novel nano-scale alignment technique based on moiré signal for room-temperature imprint lithography in the submicron realm is proposed. The moiré signals generated by two pairs of quadruple gratings on mold and wafer are optically projected onto two photo-detector arrays, then the detected moiré signals are used to estimate the alignment errors in the x and y directions. The experiment results indicate that complex differential moiré signal is sensitive to relative displacement of the mold and wafer, and the alignment accuracy obtained in the x and γ directions and in θ are 20 nm , 25 nm and 1 μrad (3σ), respectively. They can meet the requirements of alignment accuracy for submicron imprint lithography.

关键词: submicron     alignment accuracy     nano-scale alignment     quadruple     room-temperature    

Modeling of semi-rigid beam-to-column steel joints under extreme loading

C FANG, B A IZZUDDIN, A Y ELGHAZOULI, D A NETHERCOT

《结构与土木工程前沿(英文)》 2013年 第7卷 第3期   页码 245-263 doi: 10.1007/s11709-013-0215-9

摘要: Joints play an important role in providing ductility for steel-composite structures subject to extreme loading conditions, such as blast, fire and impact. Due to sound energy dissipation capability and fabrication efficiency, semi-rigid joints have increasingly received attention during the last decade. This paper presents a component approach for modeling semi-rigid beam-to-column joints based on Eurocode3, where the post-elastic response, including component strain hardening and ultimate rotational capacity, is also considered. Failure criteria are defined based on the ultimate deformation capacity of components and bolt-rows. The model enables a direct integration of joint response into global frame models with the consideration of axial deformability, such that the interaction between bending moment and axial force within the joints can be realistically captured. In addition, elevated temperature can be considered in the joint model via the degradation of the component response. Through comparisons with available test data, the joint model is shown to have good accuracy, and the failure criteria are found to be reliable yet conservative. The strain hardening response of components is shown to have significant influence on the ultimate bending capacity of the joints, while neglecting it usually leads to a conservative prediction.

关键词: semi-rigid joint     component method     ductility     elevated temperature    

Thermal buckling behavior of laminated composite plates: a finite-element study

Houdayfa OUNIS,Abdelouahab TATI,Adel BENCHABANE

《机械工程前沿(英文)》 2014年 第9卷 第1期   页码 41-49 doi: 10.1007/s11465-014-0284-z

摘要:

In this paper, the thermal buckling behavior of composite laminated plates under a uniform temperature distribution is studied. A finite element of four nodes and 32 degrees of freedom (DOF), previously developed for the bending and mechanical buckling of laminated composite plates, is extended to investigate the thermal buckling behavior of laminated composite plates. Based upon the classical plate theory, the present finite element is a combination of a linear isoparametric membrane element and a high precision rectangular Hermitian element. The numerical implementation of the present finite element allowed the comparison of the numerical obtained results with results obtained from the literature: 1) with element of the same order, 2) the first order shear deformation theory, 3) the high order shear deformation theory and 4) the three-dimensional solution. It was found that the obtained results were very close to the reference results and the proposed element offers a good convergence speed. Furthermore, a parametrical study was also conducted to investigate the effect of the anisotropy of composite materials on the critical buckling temperature of laminated plates. The study showed that: 1) the critical buckling temperature generally decreases with the increasing of the modulus ratio EL/ET and thermal expansion ratio αT/αL, and 2) the boundary conditions and the orientation angles significantly affect the critical buckling temperature of laminated plates.

关键词: thermal buckling     laminated composite plates     anisotropy     critical buckling temperature     finite-element method     high precision rectangular Hermitian element    

Emerging challenges to structural integrity technology for high-temperature applications

TU Shantung

《机械工程前沿(英文)》 2007年 第2卷 第4期   页码 375-387 doi: 10.1007/s11465-007-0066-y

摘要: Structural integrity technology has been widely used with great success for the design, manufacture and failure prevention of modern constructions such as chemical and petrochemical plants, power generation and energy conversion systems, as well as space and oceanic exploration. The modern needs of structural integrity technology are largely attributed to the increase of service temperature of the structures that results in the efficiency improvement in energy conversion and chemical processing technologies. Besides the needs arising from large-scale high-temperature plants, the high tech developments, such as micro chemo-mechanical systems and high-power electronics, provide new challenges to structural integrity technology. The present paper summarizes the recent technical progresses in large process plants and the aviation industry, micro chemo-mechanical systems, fuel cells, high-temperature electronics, and packaging and coating technologies. The state-of-the-art of structural integrity technology for high temperature applications is reviewed. Suggestions are provided for the improvement of current design and assessment methods.

关键词: manufacture     aviation industry     conversion     petrochemical     temperature    

Effects of temperature on pyrolysis products of oil sludge

LIU Jianguo, SONG Wei, NIE Yongfeng

《环境科学与工程前沿(英文)》 2008年 第2卷 第1期   页码 8-14 doi: 10.1007/s11783-008-0030-z

摘要: Temperature is the determining factor of pyrolysis, which is one of the alternative technologies for oil sludge treatment. The effects of final operating temperature ranging from 350 to 550°C on pyrolysis products of oil sludge were studied in an externally-heating fixed bed reactor. With an increase of temperature, the mass fraction of solid residues, liquids, and gases in the final product is 67.00%–56.00%, 25.60%–32.35%, and 7.40%–11.65%, and their corresponding heat values are 34.4–13.8 MJ/kg, 44.41–46.6 MJ/kg, and 23.94–48.23 MJ/Nm, respectively. The mass and energy tend to shift from solid to liquid and gas phase (especially to liquid phase) during the process, and the optimum temperature for oil sludge pyrolysis is 500°C. The liquid phase is mainly composed of alkane and alkene (C–C), and the gas phase is dominantly HC and H.

关键词: sludge treatment     corresponding     Temperature     liquid     process    

Phase separation time/temperature dependence of thermoplastics-modified thermosetting systems

ZHANG Xiujuan, XU Yuanze, YI Xiaosu

《化学科学与工程前沿(英文)》 2008年 第2卷 第3期   页码 276-285 doi: 10.1007/s11705-008-0057-5

摘要: The cure-induced phase separation processes of various thermoplastics(TP)-modified thermosetting systems which show upper critical solution temperature (UCST) or lower critical solution temperature (LCST) were studied with emphasis on the temperature dependency of the phase separation time and its potential application in the cure time-temperature processing window. We found that the phase separation time/temperature relationship follows the simple Arrhenius equation. The cure-induced phase separation activation energy (ps) generated from the linear fitting of the Arrhenius equation is irrelevant to the detection means of phase separation time. We also found that (ps) is insensitive to TP content, TP molecular weight and curing rate, but it changes with the cure reaction kinetics and the chemical environment of the systems. With the established phase separation time-temperature dependence relation, we can easily establish the whole cure time-temperature transformation (TTT) diagram with morphology information which is a useful map for the TP/TS composites processing industry.

关键词: separation time-temperature     temperature dependency     cure-induced     separation activation     temperature    

Elevated temperature creep model of parallel wire strands

《结构与土木工程前沿(英文)》   页码 1060-1071 doi: 10.1007/s11709-023-0981-y

摘要: Parallel wire strands (PWSs), which are widely used in prestressed steel structures, are typically in high-stress states. Under fire conditions, significant creep effects occur, reducing the prestress and influencing the mechanical behavior of PWSs. As there is no existing approach to analyze their creep behavior, this study experimentally investigated the elevated temperature creep model of PWSs. A charge-coupled camera system was incorporated to accurately obtain the deformation of the specimen during the elevated temperature creep test. It was concluded that the temperature level had a more significant effect on the creep strain than the stress level, and 450 °C was the key segment point where the creep rate varied significantly. By comparing the elevated temperature creep test results for PWSs and steel strands, it was found that the creep strain of PWSs was lower than that of steel strands at the same temperature and stress levels. The parameters in the general empirical formula, the Bailey–Norton model, and the composite time-hardening model were fitted based on the experimental results. By evaluating the accuracy and form of the models, the composite time-hardening model, which can simultaneously consider temperature, stress, and time, is recommended for use in the fire-resistance design of pre-tensioned structures with PWSs.

关键词: parallel wire strands     experimental study     elevated temperature creep model    

标题 作者 时间 类型 操作

Crack detection for wading-concrete structures using water irrigation and electric heating

期刊论文

Optimizing the configuration of a clearwell by integrating pilot and full-scale tracer testing

LIU Wenjun, DU Zhipeng, JIN Junwei

期刊论文

Real-time tool condition monitoring method based on temperature measurement and artificial neural network

期刊论文

彩色测温方法中物体辐射色域的界定和划分

王安全,程晓舫,陆少松

期刊论文

Performance of a bi-layer solar steam generation system working at a high-temperature of top surface

Jinxin ZHONG, Congliang HUANG

期刊论文

Room temperature preparation of hydrazine-linked covalent organic frameworks coated capillaries for

期刊论文

An optimized solar-air degree-day method to evaluate energy demand for poultry buildings in different

Yang WANG, Baoming LI

期刊论文

利用六氟化硫示踪技术预估不同年龄阶段的放牧荷斯坦奶牛甲烷排放量

Steven J. Morrison, Judith McBride, Alan W. Gordon, Alastair R. G. Wylie, 闫天海

期刊论文

A nano-scale alignment method for imprint lithography

WANG Li, LU Bing-heng, DING Yu-cheng, QIU Zhi-hui, LIU Hong-zhong

期刊论文

Modeling of semi-rigid beam-to-column steel joints under extreme loading

C FANG, B A IZZUDDIN, A Y ELGHAZOULI, D A NETHERCOT

期刊论文

Thermal buckling behavior of laminated composite plates: a finite-element study

Houdayfa OUNIS,Abdelouahab TATI,Adel BENCHABANE

期刊论文

Emerging challenges to structural integrity technology for high-temperature applications

TU Shantung

期刊论文

Effects of temperature on pyrolysis products of oil sludge

LIU Jianguo, SONG Wei, NIE Yongfeng

期刊论文

Phase separation time/temperature dependence of thermoplastics-modified thermosetting systems

ZHANG Xiujuan, XU Yuanze, YI Xiaosu

期刊论文

Elevated temperature creep model of parallel wire strands

期刊论文