共查询到20条相似文献，搜索用时 15 毫秒
1.
Sheng Yan Jun Zhang Huaying Chen Gursel Alici Haiping Du Yonggang Zhu Weihua Li 《Biomicrofluidics》2014,8(6)
Microfluidic diagnostic devices often require handling particles or cells with different sizes. In this investigation, a tunable hydrophoretic device was developed which consists of a polydimethylsiloxane (PDMS) slab with hydrophoretic channel, a PDMS diaphragm with pressure channel, and a glass slide. The height of the hydrophoretic channel can be tuned simply and reliably by deforming the elastomeric diaphragm with pressure applied on the pressure channel. This operation allows the device to have a large operating range where different particles and complex biological samples can be processed. The focusing performance of this device was tested using blood cells that varied in shape and size. The hydrophoretic channel had a large cross section which enabled a throughput capability for cell focusing of ∼15 000 cells s−1, which was more than the conventional hydrophoretic focusing and dielectrophoresis (DEP)-active hydrophoretic methods. This tunable hydrophoretic focuser can potentially be integrated into advanced lab-on-a-chip bioanalysis devices. 相似文献
2.
Keith N. Hampton 《The Information Society》2003,19(5):417-428
Critics have argued that information and communication technologies (ICTs) disconnect people from their social networks and reduce public participation. Research in support of this perspective has been biased by two assumptions. The first is a tendency to privilege the Internet as a social system removed from the other ways people communicate. The second is a tendency to favor broadly supportive strong social ties. Survey and ethnographic observations from Netville, a 2-year community networking experiment, suggest that weak, not strong ties experience growth as a result of ICTs. By examining a unique and underexplored stage in the life cycle of a community networking project, the end of a networking trial, this article demonstrates how ICTs facilitate community participation and collective action (a) by creating large, dense networks of relatively weak social ties and (b) through the use of ICTs as an organizing tool. 相似文献
3.
This paper addresses the role of knowledge metaphors in knowledge sharing interventions. Open space can be treated as a specific technology for blending knowledge sources and as a broader knowledge metaphor that focuses on self-regulating knowledge processes. The paper outlines the experience of applying the open space technology in a large-scale civic society initiative, ‘My Estonia’, in 2009 and 2010. The study reveals contradictions between different meanings of open space in the knowledge sharing context. The validity of the mapping of the open space metaphor depends on the adjustment of the open space technology to the composition of the team. It can be increased by the freedom to initiate new think tanks in different locations, and thus link mental and physical open space activities. Encouraging mobility of participants and continuing think tank activities by applying virtual communication tools reflects a broader interpretation of the open space metaphor. 相似文献
4.
The objective of this paper is to take an in-depth look, from a network perspective, at the role that social capital plays in improving knowledge exchange between organizations. To do this, we consider the three dimensions of social capital: the structural dimension, as measured by the position of firms bridging structural holes; the relational dimension, as gauged by the level of trust and friendship in each relationship; and the cognitive dimension, as estimated by the presence of a shared culture. We also evaluate the level of organizational and human capital present in terms of the firms in the network. Empirical evidence has been gathered from the Madrid Science Park in Spain by applying the social network analysis methodology. The results show that the three dimensions of social capital play a significant role in increasing knowledge exchange in this network, while human and organizational capital differences are only significant for a sub-sample. 相似文献
5.
Harold Borko 《Information processing & management》1977,13(6):355-365
A theory of indexing helps explain the nature of indexing, the structure of the vocabulary, and the quality of the index. Indexing theories formulated by Jonker, Heilprin, Landry and Salton are described. Each formulation has a different focus. Jonker, by means of the Terminological and Connective Continua, provided a basis for understanding the relationships between the size of the vocabulary, the hierarchical organization, and the specificity by which concepts can be described. Heilprin introduced the idea of a search path which leads from query to document. He also added a third dimension to Jonker's model; the three variables are diffuseness, permutivity and hierarchical connectedness. Landry made an ambitious and well conceived attempt to build a comprehensive theory of indexing predicated upon sets of documents, sets of attributes, and sets of relationships between the two. It is expressed in theorems and by formal notation. Salton provided both a notational definition of indexing and procedures for improving the ability of index terms to discriminate between relevant and nonrelevant documents. These separate theories need to be tested experimentally and eventually combined into a unified comprehensive theory of indexing. 相似文献
6.
Trapping single human osteoblast-like cells from a heterogeneous population using a dielectrophoretic microfluidic device 总被引：1，自引：0，他引：1
We describe a system for the isolation, concentration, separation, and recovery of human osteoblast-like cells from a heterogeneous population using dielectrophoretic ring traps. Cells flowing in a microfluidic channel are immobilized inside an electric field cage using negative dielectrophoresis. A planar ring electrode creates a closed trap while repelling surrounding cells. Target cells are identified by fluorescent labeling, and are trapped as they pass across a ring electrode by an automated system. We demonstrate recovery of small populations of human osteoblast-like cells with a purity of 100%, which in turn demonstrates the potential of such a device for cell selection from a heterogeneous population. 相似文献
7.
Neither traditional philosophy nor current applied ethics seem able to cope adequately with the highly dynamic character of our modern technological culture. This is because they have insufficient insight into the moral significance of technological artifacts and systems. Here, much can be learned from recent science and technology studies (STS). They have opened up the black box of technological developments and have revealed the intimate intertwinement of technology and society in minute detail. However, while applied ethics is characterized by a certain "technology blindness," the most influential approaches within STS show a "normative deficit" and display on agnostic or even antagonistic attitude toward ethics. To repair the blind spots of both applied ethics and STS, the authors sketch the contours of a pragmatist approach. They will explore the tasks and tools of a pragmatist ethics and pay special attention to the exploration of future worlds disclosed and shaped by technology and the management of deep value conflicts inherent in a pluralistic society. 相似文献
8.
Edward C. Ting 《Journal of The Franklin Institute》1973,296(2):77-89
Unbonded beams supported by a foundation are studied. The foundation is assumed that tensile stresses cannot be transmitted across the interface between beams and their supporting subgrade. The subgrade is characterized by a two-parameter model proposed by Vlasov and Leont'ev, Pasternak and Filonenko-Borodich. Thus the shear strength of the foundation material is taken into account. With a suitable choice of parameters, analytical solutions are obtained and compared to experimental results reported by Durelli et al. The effects of the “lift up” of the beam and a discussion of the foundation parameters are also presented. 相似文献
9.
Recently, series elasticity has been realized using pneumatics in human-robot interaction systems. Pneumatic circuits provide not only a flexible power transmission, but also the elastic element in a series elastic actuator (SEA). Pneumatic series elastic systems involve more than twice the number of parameters that influence system behaviors in comparison with rigid robotic systems. In this study, a position controller that eliminates the need of identifying a system model by employing the time delay estimation (TDE) technique is proposed for pneumatic SEA systems. The TDE technique is effective in compensating for system dynamics and all uncertainties involved in system behaviors without imposing computation load. TDE error is cancelled out through a learning way, which improves control performance and leads to asymptotic stability. A simulation study demonstrates the robustness of the proposed controllers against uncertainties imposed on the motor system as well as uncertainties on the end-effector. The simulation shows the efficacy of the learning compensation for TDE error. 相似文献
10.
Sergio Bittanti Fabio Romeo Riccardo Scattolini 《Journal of The Franklin Institute》1984,318(1):29-56
In this paper, an extended simulation study is presented by which the power of modern digital identification and control methodology is tested against the nontrivial dynamics of a relatively simple yet nonelementary plant. Many critical issues which may significantly affect the success of the entire design process can be discussed along the lines of this study. The plant considered here is a liquid-saturated steam heat exchanger, where the liquid flow-rate is manipulated to regulate the outlet liquid temperature. All the numerical experiments have been conducted by digital simulation of a fairly standard nonlinear distributed parameter model. 相似文献
11.
《中国科学院院刊(英文版)》2008,22(1):13-14
Aresearch project on the greenhouse cultivation of Swertia chirayita Buch Ham, a popular herbal drug used by the Tibetan people against liver and gallbladder diseases, recently passed the acceptance check by a panel of experts under the auspices of Qinghai Provincial S＆T Bureau. The feat was accomplished by researchers from the Lanzhoubased CAS Northwest Institute of Plateau Biology. 相似文献
12.
Creating knowledge within a team for developing new products and services is considered a primary means for improving organizational performance. Drawing upon the socio-technical perspective, we investigate the blended effects of social (learning culture, teamwork quality, and knowledge complexity) and technical (IT support) factors on team-level knowledge creation and team performance. We propose a model that features synergetic interactions between social and technical factors in this knowledge creation process. The model was tested by utilizing data from a field survey of industry managers. The results show significant interactions between social and technical factors, which influence team-level knowledge creation and, in turn, team performance. Our findings can be used to develop socio-technical initiatives to enhance the process of creating team-level knowledge within firms. 相似文献
13.
Davison and Ramesh expressed equivalently the condition for the characteristic roots of a real matrix to lie within a sector by the condition for a matrixof doubled order to be Hurwitzian (1). A further generalization of their result is given in this note. 相似文献
14.
15.
There is a high demand to develop and incorporate decision support tools, by the transportation sectors and other concerned agencies, to improve their infrastructure assets management under shrinking budgets and increasing demands. This paper develops a proof-of-concept Bayesian belief network (BBN) model to rank roads in a network system based on several key performance indicators (KPI) using a probabilistic framework. For a given road network, the proposed tool is capable of ranking or prioritizing the segment of roads for high level management objectives. To demonstrate the application of the proposed model, various scenarios are elaborated and discussed in detail. Finally, the sensitivity analysis is carried out to evaluate the effects of different KPIs. 相似文献
16.
Emilie Weibull Shunsuke Matsui Manabu Sakai Helene Andersson Svahn Toshiro Ohashi 《Biomicrofluidics》2013,7(6)
Understanding biomolecular gradients and their role in biological processes is essential for fully comprehending the underlying mechanisms of cells in living tissue. Conventional in vitro gradient-generating methods are unpredictable and difficult to characterize, owing to temporal and spatial fluctuations. The field of microfluidics enables complex user-defined gradients to be generated based on a detailed understanding of fluidic behavior at the μm-scale. By using microfluidic gradients created by flow, it is possible to develop rapid and dynamic stepwise concentration gradients. However, cells exposed to stepwise gradients can be perturbed by signals from neighboring cells exposed to another concentration. Hence, there is a need for a device that generates a stepwise gradient at discrete and isolated locations. Here, we present a microfluidic device for generating a stepwise concentration gradient, which utilizes a microwell slide''s pre-defined compartmentalized structure to physically separate different reagent concentrations. The gradient was generated due to flow resistance in the microchannel configuration of the device, which was designed using hydraulic analogy and theoretically verified by computational fluidic dynamics simulations. The device had two reagent channels and two dilutant channels, leading to eight chambers, each containing 4 microwells. A dose-dependency assay was performed using bovine aortic endothelial cells treated with saponin. High reproducibility between experiments was confirmed by evaluating the number of living cells in a live-dead assay. Our device generates a fully mixed fluid profile using a simple microchannel configuration and could be used in various gradient studies, e.g., screening for cytostatics or antibiotics. 相似文献
17.
This study presents a method for density-based separation of monodisperse encapsulated cells using a standing surface acoustic wave (SSAW) in a microchannel. Even though monodisperse polymer beads can be generated by the state-of-the-art technology in microfluidics, the quantity of encapsulated cells cannot be controlled precisely. In the present study, mono-disperse alginate beads in a laminar flow can be separated based on their density using acoustophoresis. A mixture of beads of equal sizes but dissimilar densities was hydrodynamically focused at the entrance and then actively driven toward the sidewalls by a SSAW. The lateral displacement of a bead is proportional to the density of the bead, i.e., the number of encapsulated cells in an alginate bead. Under optimized conditions, the recovery rate of a target bead group (large-cell-quantity alginate beads) reached up to 97% at a rate of 2300 beads per minute. A cell viability test also confirmed that the encapsulated cells were hardly damaged by the acoustic force. Moreover, cell-encapsulating beads that were cultured for 1 day were separated in a similar manner. In conclusion, this study demonstrated that a SSAW can successfully separate monodisperse particles by their density. With the present technique for separating cell-encapsulating beads, the current cell engineering technology can be significantly advanced. 相似文献
18.
《Journal of The Franklin Institute》2021,358(18):9561-9586
In this paper a novel adaptive robust fault-tolerant sync control method is proposed for a two-slider system where two sliders are constrained by a flexible beam. At first the dynamic models of sync motion system subject to external disturbances and actuator faults are derived. In order to avoid the shortcomings of truncated model, the model of flexible beam is described by using infinite dimensional equation. Then based on the models a novel disturbance observer and an adaptive fault-tolerant control law are designed. The disturbance observer is used to estimate and cancel external disturbances. The adaptive fault-tolerant control is used to deal with the partial loss of effectiveness faults. Lyapunov functional approach is used to prove that the closed-loop system with the proposed control laws is uniformly bounded stable. Finally, some simulation results display that the proposed control laws can obtain excellent sync performance in the present of external disturbances and actuator partial loss of effectiveness faults. 相似文献
19.
Jang K Xu Y Tanaka Y Sato K Mawatari K Konno T Ishihara K Kitamori T 《Biomicrofluidics》2010,4(3):32208
Recently, interest in single cell analysis has increased because of its potential for improving our understanding of cellular processes. Single cell operation and attachment is indispensable to realize this task. In this paper, we employed a simple and direct method for single-cell attachment and culture in a closed microchannel. The microchannel surface was modified by applying a nonbiofouling polymer, 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer, and a nitrobenzyl photocleavable linker. Using ultraviolet (UV) light irradiation, the MPC polymer was selectively removed by a photochemical reaction that adjusted the cell adherence inside the microchannel. To obtain the desired single endothelial cell patterning in the microchannel, cell-adhesive regions were controlled by use of round photomasks with diameters of 10, 20, 30, or 50 μm. Single-cell adherence patterns were formed after 12 h of incubation, only when 20 and 30 μm photomasks were used, and the proportions of adherent and nonadherent cells among the entire UV-illuminated areas were 21.3%±0.3% and 7.9%±0.3%, respectively. The frequency of single-cell adherence in the case of the 20 μm photomask was 2.7 times greater than that in the case of the 30 μm photomask. We found that the 20 μm photomask was optimal for the formation of single-cell adherence patterns in the microchannel. This technique can be a powerful tool for analyzing environmental factors like cell-surface and cell-extracellular matrix contact. 相似文献
20.
We extend the Profit from Innovation (PFI) framework (Teece, 1986) by combining it with open innovation insights: we explore when and how managers make the transition between closed and open innovation, and how they use appropriation (formal and informal defense mechanisms) and project strategies to capture the value generated from the innovation at the project level. Based on a radical innovation project at Jaguar (UK), we contribute to a process and temporal perspective of open innovation by shedding light on two core project processes and their enabling mechanisms which influenced the ability of Jaguar to maximize profits from the innovation. The first core project process was the choice of timing of the shift from a closed to an open model of innovation: it was enabled by a pro-active change in the formal defense strategy (i.e. submission of a patent), and by an internal loose coupling project strategy that involved autonomy of the project champion and internal engineers’ weak membership in the project. The second core process was an external loose coupling project strategy that was enabled by the deployment of two complementary informal appropriation mechanisms namely, the reduction of the scope of tasks allocated to external partners combined with the development of guarded relationships with them. 相似文献