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251.
This paper investigates the feasibility to achieve grinding-hardening in a plunge cylindrical grinding process. To understand the mechanisms, a temperature-dependent finite element heat transfer model incorporating a triangular moving heat source was developed to describe the temperature field, thus to predict the thickness of the grinding-hardened layer. The analysis carried out included the variation effect of depth of cut caused by the change in wheel-workpiece engagement. The model was applied on quenchable steel 1045 and the analysis was verified experimentally. It was shown that the heating cycle in plunge cylindrical grinding is the result of consecutive heating and cooling processes, varying from location to location in a workpiece. The ratio of the workpiece speed to the infeed rate plays an important role in the heat treatment cycle. 相似文献
252.
Baolai Liang Ping-Show Wong Thai Tran Vitaliy G. Dorogan Yuriy I. Mazur Morgan E. Ware Gregory J. Salamo Chih-Kang Shih Diana L. Huffaker 《Nano Research》2013,6(4):235-242
We report on InGaAs quantum disks (QDks) controllably formed on the top (001) facet of nano-patterned GaAs pyramidal platforms. The QDks exhibit pyramidal shape with special facets and varied dimensions, depending on the GaAs pyramidal buffer and the amount of InGaAs deposited. The formation of QDks is explained by the overgrowth of an InGaAs layer and thereafter coalescence of small InGaAs islands. Photoluminescence (PL) characteristics of ensemble QDks and exciton features of individual QDks together demonstrate that we may achieve a transition from zero-dimensional (0D) to two-dimensional (2D) quantum structure with increasing QDk size. This transition provides the flexibility to continuously tailor the dimensionality and subsequently the quantum confinement of semiconductor nanostructures via site-controlled self-assembled epitaxy for device applications based on single quantum structures. 相似文献
253.
Stephan K Kelly M McClure R Seubsman SA Yiengprugsawan V Bain C Sleigh A;Thai Cohort Study Team 《Accident; analysis and prevention》2011,(3):1062-1067
Background
A major barrier to addressing the problem of transport injury in low to middle-income countries is the lack of information regarding the incidence of traffic crashes and the demographic, behavioural and socio-economic determinants of crash-related injury. This study aimed to determine the baseline frequency and distribution of transport injury and the prevalence of various road safety behaviours in a newly recruited cohort of Thai adults.Methods
The Thai Health-Risk Transition Study includes an ongoing population-based cohort study of 87,134 adult students residing across Thailand. Baseline survey data from 2005 includes data on self-reported transport injury within the previous 12 months and demographic, behavioural and transportation factors that could be linked to Thailand's transport risks.Results
Overall, 7279 (8.4% or 8354 per 100,000) of respondents reported that their most serious injury in the 12 months prior to recruitment in the cohort was transport-related, with risk being higher for males and those aged 15–19 years. Most transport injuries occurred while using motorcycles. A much higher proportion of males reported driving after three or more glasses of alcohol at least once in the previous year compared to females. The prevalence of motorcycle helmet and seat belt wearing in this sample were higher than previously reported for Thailand.Conclusions
The reported data provide the basis for monitoring changes in traffic crash risks and risk behaviours in a cohort of adults in the context of ongoing implementation of policy and programs that are currently being introduced to address the problem of transport-related injury in Thailand. 相似文献254.
Robert Braunsdorf Uwe Hener Gaby Przibilla Steffen Piecha und Armin Mosandl 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1993,197(1):24-28
Zusammenfassung Der Einfluß chromatographischer und technologischer Verfahren auf den13C-Isotopengehalt aromarelevanter Substanzen in Orangenölen wird untersucht. Um Fehlinterpretationen von Isotopendaten auszuschließen, muß eine effektive, verlustfreie Probenaufbereitung sichergestellt werden. Während bei der Verarbeitung einfacher sowie terpenarmer (entterpenisierter) Orangenöle keine Isotopendiskriminierung auftritt, sind bei Spezialprodukten, bei denen einzelne Substanzen Konzentrationen von >70% erreichen, Abweichungen des13C/12C-Isotopenverhältnisses feststellbar.
The influence of analytical and technological procedures on the13C/12C isotope ratio of orange oil compounds
The influence of Chromatographic and technological procedures on the13C-isotope value of flavour compounds from orange oils was investigated. In order to avoid misinterpretations of isotopic data, quantitative yields during sample clean-up must be ascertained. Ordinary as well as deterpenated orange oils were not influenced by the technological processing. In the case of special products containing single compounds concentrated up to more than 70%, a shift in the13C/12C-isotope ratio was detectable.相似文献
255.
Steve Schneider Thai Son Hoang Ken Robinson Helen Treharne 《Formal Aspects of Computing》2006,18(3):308-328
The introduction of probabilistic behaviour into the B-method is a recent development. In addition to allowing probabilistic behaviour to be modelled, the relationship between expected values of the machine state can be expressed and verified. This paper explores the application of probabilistic B to a simple case study: tracking the volume of liquid held in a tank by measuring the flow of liquid into it. The flow can change as time progresses, and sensors are used to measure the flow with some degree of accuracy and reliability, modelled as non-deterministic and probabilistic behaviour respectively. At the specification level, the analysis is concerned with the expectation clause in the probabilistic B machine and its consistency with machine operations. At the refinement level, refinement and equivalence laws on probabilistic GSL are used to establish that a particular design of sensors delivers the required level of reliability. 相似文献
256.
Gaby junowicz 《通讯世界》2004,(3):42
移动运营商推出3G业务的道路上存在着很多困难,其中最为严峻的挑战莫过于建立既能支持现有2G网络,又能为下一代用户提供广泛业务的移动基础设施.由于一段时期内,2G业务仍是移动运营商的主要收入流,因此移植到UMTS或者EDGE等更高速率的分组交换网,需要同时管理运行两种异构网络. 相似文献
257.
Kyoung Kwan Ahn Nguyen Huynh Thai Chau 《Journal of Mechanical Science and Technology》2007,21(8):1196-1206
Pneumatic cylinders are one kind of low cost actuation sources which have been applied in industrial and robotics field, since
they have a high power/weight ratio, a high-tension force and a long durability. To overcome the shortcomings of conventional
pneumatic cylinders, a number of newer pneumatic actuators have been developed such as McKibben Muscle, Rubber Actuator and
Pneumatic Artificial Muscle (PAM) Manipulators. However, some limitations still exist, such as the air compressibility and
the lack of damping ability of the actuator bring the dynamic delay of the pressure response and cause the oscillatory motion.
In addition, the nonlinearities in the PAM manipulator still limit the controllability. Therefore, it is not easy to realize
motion with high accuracy and high speed and with respect to various external inertia loads.
To overcome these problems, a novel controller which harmonizes a phase plane switching control method (PPSC) with conventional
PID controller and the adaptabilities of neural network is newly proposed. In order to realize satisfactory control performance
a variable damper, Magneto-Rheological Brake (MRB), is equipped to the joint of the robot. The mixture of conventional PID
controller and an intelligent phase plane switching control using neural network (IPPSC) brings us a novel controller. The
experiments were carried out in a robot arm, which is driven by two PAM actuators, and the effectiveness of the proposed control
algorithm was demonstrated through experiments, which had proved that the stability of the manipulator can be improved greatly
in a high gain control by using MRB with 1PPSC and without regard for the changes of external inertia loads. 相似文献
258.
Chien H. Thai H. Nguyen‐Xuan N. Nguyen‐Thanh T‐H. Le T. Nguyen‐Thoi T. Rabczuk 《International journal for numerical methods in engineering》2012,91(6):571-603
This paper presents a novel numerical procedure based on the framework of isogeometric analysis for static, free vibration, and buckling analysis of laminated composite plates using the first‐order shear deformation theory. The isogeometric approach utilizes non‐uniform rational B‐splines to implement for the quadratic, cubic, and quartic elements. Shear locking problem still exists in the stiffness formulation, and hence, it can be significantly alleviated by a stabilization technique. Several numerical examples are presented to show the performance of the method, and the results obtained are compared with other available ones. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
259.
Free vibration of axially loaded rectangular composite beams with arbitrary lay-ups using refined shear deformation theory is presented. It accounts for the parabolical variation of shear strains through the depth of beam. Three governing equations of motion are derived from the Hamilton’s principle. The resulting coupling is referred to as triply axial-flexural coupled vibration. A displacement-based one-dimensional finite element model is developed to solve the problem. Numerical results are obtained for rectangular composite beams to investigate effects of fiber orientation and modulus ratio on the natural frequencies, critical buckling loads and load–frequency curves as well as corresponding mode shapes. 相似文献
260.
Dieu Phuong Nguyen Thi Dieu Linh Tran Phuong Le Thi Ki Dong Park Thai Thanh Hoang Thi 《International journal of molecular sciences》2021,22(16)
Cordyline terminalis leaf extract (aqCT) possesses abundant polyphenols and other bioactive compounds, which are encapsulated in gelatin–polyethylene glycol–tyramine (GPT)/alpha-cyclodextrin (α-CD) gels to form the additional functional materials for biomedical applications. In this study, the gel compositions are optimized, and the GPT/α-CD ratios equal to or less than one half for solidification are found. The gelation time varies from 40.7 min to 5.0 h depending on the increase in GPT/α-CD ratios and aqCT amount. The aqCT extract disturbs the hydrogen bonding and host–guest inclusion of GPT/α-CD gel networks, postponing the gelation. Scanning electron microscope observation shows that all gels with or without aqCT possess a microarchitecture and porosity. GPT/α-CD/aqCT gels could release polyphenols from 110 to 350 nmol/mL at the first hour and sustainably from 5.5 to 20.2 nmol/mL for the following hours, which is controlled by feeding the aqCT amount and gel properties. GPT/α-CD/aqCT gels achieved significant antioxidant activity through a 100% scavenging DPPH radical. In addition, all gels are non-cytotoxic with a cell viability more than 85%. Especially, the GPT3.75α-CD10.5aqCT gels with aqCT amount of 3.1–12.5 mg/mL immensely enhanced the cell proliferation of GPT3.75α-CD10.5 gel without extract. These results suggest that the inherent bioactivities of aqCT endowed the resulting GPT/α-CD/aqCT gels with effective antioxidant and high biocompatibility, and natural polyphenols sustainably release a unique platform for a drug delivery system or other biomedical applications. 相似文献