36,979 research outputs found
Experimental analysis of the influence of wall axial conduction on gas-to-gas micro heat exchanger effectiveness
No full textIn this paper an experimental investigation of the thermal performances of gas-to-gas micro heat
exchangers operating under different flow configurations (co-current, counter-current, cross flow) is presented
and the results are compared with the predictions of the conventional correlations developed for
the design of the conventional-sized heat exchangers. A double-layered microchannel heat exchanger has
been specifically designed in order to be able to reproduce co-current, counter-current and cross flow gas
arrangements. The core is housed in a shell made of polymer; on the contrary, the foil between the hot
and cold flow is exchangeable; several foils made with different materials (copper, peek, stainless steel
and aluminum) and with different thickness have been investigated in order to put in evidence the effect
due to the axial wall-fluid conjugate heat transfer on the thermal efficiency of the micro heat exchanger.
The results show that the conjugate heat transfer can be very strong in micro heat exchangers and it
tends to reduce the effectiveness of counter-current micro heat exchangers and to increase the effectiveness
of cross flow micro heat exchangers. In the case of a co-current arrangement with balanced flows the
role of the wall axial conduction can be considered negligible
Experimental and numerical investigation of forced convection of subsonic gas flows in microtubes
No full textThe aim of this paper is to investigate the impact of gas compressibility on forced convection through
commercial stainless steel microtubes with an inner diameter of 750 lm, 510 lm and 170 lm by combining
experimental data with numerical simulations. The analysis covers both transitional and turbulent
flow regimes (3000 < Re < 12,000). The results have evidenced that compressibility effects can significantly
enhance convective heat transfer when the gas flow is heated by the walls (H boundary condition).
This enhancement turns out to be more remarkable for microtubes with smaller inner diameter (lower
than 200 lm). In order to explore in-depth the heat transfer mechanism along the microtube in presence
of non negligible compressibility effects, the experimental data have been integrated with the numerical
results obtained by modeling the fluid flow through the microtube with the adoption of the Arbitrary–
Lagrangian–Eulerian (ALE) method and the Lam–Bremhorst Low–Reynolds number turbulence model
in order to evaluate eddy viscosity coefficient and turbulence energy within the gas flow. The results presented
in this work put in evidence that the integration of the experimental data with the numerical
results is strongly beneficial in order to obtain a deep investigation of the physics of micro convection
for compressible flows. The experimental values of the Nusselt numbers obtained for three different
microtubes have been compared with both classical correlations validated for conventional pipes and
specific correlations proposed for microtubes. This comparison highlights that the conventional correlations
still holds for gas flow convection through microtubes when the compressibility effect is not significant.
On the contrary, when compressibility is no longer negligible, the conventional correlations tend to
underestimate the value of the Nusselt number. It is also demonstrated that the specific correlations proposed
for the prediction of the Nusselt number in microtubes fail in presence of strong compressibility
effects
A new cavefish species from Southwest China, Sinocyclocheilus gracilicaudatus sp. nov. (Teleostei: Cypriniformes: Cyprinidae)
No full textWang, Dan, Zhao, Yahui, Yang, Junxing, Zhang, Chunguang (2014): A new cavefish species from Southwest China, Sinocyclocheilus gracilicaudatus sp. nov. (Teleostei: Cypriniformes: Cyprinidae). Zootaxa 3768 (5): 583-590, DOI: 10.11646/zootaxa.3768.5.
Design and Experimental Investigation of A Gas-To-Gas Counter Flow Micro Heat Exchanger
No full textIn this work, a double-layered microchannel heat exchanger is designed for investigation on
gas-to-gas heat transfer. The micro-device contains 133 parallel microchannels machined
into a polished polyether ether ketone plate for both the hot side and cold side. The
microchannels are 200mm high, 200mm wide, and 39.8mm long. The design of the microdevice
allows tests with partition foils in different materials and of flexible thickness. A test
rig is developed with the integration of customized pressure and temperature sensors for
in situ measurements. Experimental tests on the counter-flow micro heat exchanger have
been carried out for five different partition foils and various mass flow rates. The
experimental results, in terms of pressure drop, heat transfer coefficients, and heat
exchanger effectiveness are discussed and compared with the predictions of the classic theory
for conventionally sized heat exchangers
sj-pdf-1-dos-10.1177_15593258211067060 – Supplemental Material for Serum Metabolomic Analysis of Radiation-Induced Lung Injury in Rats
No full textSupplemental Material, sj-pdf-1-dos-10.1177_15593258211067060 for Serum Metabolomic Analysis of Radiation-Induced Lung Injury in Rats by Yahui Feng, Yiying Gao, Wenling Tu, Yang Feng, Jianping Cao and Shuyu Zhang in Dose-Response</p
Special issue: Process safety in times of a pandemic
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Safety and Security Scienc
Distributed human computation framework for linked data co-reference resolution
No full textDistributed Human Computation (DHC) is a technique used to solve computational problems by incorporating the collaborative effort of a large number of humans. It is also a solution to AI-complete problems such as natural language processing. The Semantic Web with its root in AI is envisioned to be a decentralised world-wide information space for sharing machine-readable data with minimal integration costs. There are many research problems in the Semantic Web that are considered as AI-complete problems. An example is co-reference resolution, which involves determining whether different URIs refer to the same entity. This is considered to be a significant hurdle to overcome in the realisation of large-scale Semantic Web applications. In this paper, we propose a framework for building a DHC system on top of the Linked Data Cloud to solve various computational problems. To demonstrate the concept, we are focusing on handling the co-reference resolution in the Semantic Web when integrating distributed datasets. The traditional way to solve this problem is to design machine-learning algorithms. However, they are often computationally expensive, error-prone and do not scale. We designed a DHC system named iamResearcher, which solves the scientific publication author identity co-reference problem when integrating distributed bibliographic datasets. In our system, we aggregated 6 million bibliographic data from various publication repositories. Users can sign up to the system to audit and align their own publications, thus solving the co-reference problem in a distributed manner. The aggregated results are published to the Linked Data Cloud
Intersystem soft handover for converged DVB-H and UMTS networks
No full textDigital video broadcasting for handhelds (DVB-H) is the standard for broadcasting Internet Protocol (IP) data services to mobile portable devices. To provide interactive services for DVB-H, the Universal Mobile Telecommunications System (UMTS) can be used as a terrestrial interaction channel for the unidirectional DVB-H network. The converged DVB-H and UMTS network can be used to address the congestion problems due to the limited multimedia channel accesses of the UMTS network. In the converged network, intersystem soft handover between DVB-H and UMTS is needed for an optimum radio resource allocation, which reduces network operation cost while providing the required quality of service. This paper deals with the intersystem soft handover between DVB-H and UMTS in such a converged network. The converged network structure is presented. A novel soft handover scheme is proposed and evaluated. After considering the network operation cost, the performance tradeoff between the network quality of service and the network operation cost for the intersystem soft handover in the converged network is modeled using a stochastic tree and analyzed using a numerical simulation. The results show that the proposed algorithm is feasible and has the potential to be used for implementation in the real environment
Research in Nonlinearity of Surface Acoustic Wave Devices
No full textSurface acoustic wave (SAW) devices are one of the indispensable components in the radio frequency (RF) front-end of mobile phones. With the development of mobile communication technology, the requirements for linear specification of devices are more and more strict. Nonlinear distortions of SAW devices have a serious influence on the application of mobile RF modules. To satisfy the strict requirement of linearity of communication system, it is necessary to understand the generation mechanism of nonlinearity and study the accurate modeling, appropriate measurement methods, and nonlinear response elimination technology. In this paper, we summarize the research progress on the nonlinearity of SAW devices in recent years from four aspects: the generation mechanism, simulation methods, measurement system, and suppression technology. The nonlinear harmonics with the nonlinear Mason equivalent circuit model are simulated. Furthermore, harmonics and intermodulation signals of SAW filters are tested by the authors. Thanks to these research studies, it is of great significance to the development of future RF front-end modules with high linear SAW devices
Beyond interfaces: A usability study of Chinese journal databases
No full textA presentation at the Council on East Asian Libraries (CEAL) annual meeting in Boston, MA on March 21, 2007
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