Cournot Competition Yields Spatial Avoiding Competition in Groups

This paper characterizes the properties of equilibrium location patterns in an Anderson-Neven-Pal model and uses these characteristics to comprehensively find the subgame perfect Nash equilibria, most of which are not yet found in the literature. Since the external competition effect may be exactly canceled out, or internal competition strictly dominates external competition, or the internal competition effect is consistent with the external competition effect, therefore without any externality and prior collusion, a competitive group structure may form endogenously in equilibrium and firms tend to avoid competition inside each group. The analyses of an Anderson-Neven-Pal model are instructive in studying the conditions for a capacity to implement a ``Nash combination."Cournot competition; Spatial competition; Nash equilibrium

Second order closure modeling of turbulent buoyant wall plumes

Non-intrusive measurements of scalar and momentum transport in turbulent wall plumes, using a combined technique of laser Doppler anemometry and laser-induced fluorescence, has shown some interesting features not present in the free jet or plumes. First, buoyancy-generation of turbulence is shown to be important throughout the flow field. Combined with low-Reynolds-number turbulence and near-wall effect, this may raise the anisotropic turbulence structure beyond the prediction of eddy-viscosity models. Second, the transverse scalar fluxes do not correspond only to the mean scalar gradients, as would be expected from gradient-diffusion modeling. Third, higher-order velocity-scalar correlations which describe turbulent transport phenomena could not be predicted using simple turbulence models. A second-order closure simulation of turbulent adiabatic wall plumes, taking into account the recent progress in scalar transport, near-wall effect and buoyancy, is reported in the current study to compare with the non-intrusive measurements. In spite of the small velocity scale of the wall plumes, the results showed that low-Reynolds-number correction is not critically important to predict the adiabatic cases tested and cannot be applied beyond the maximum velocity location. The mean and turbulent velocity profiles are very closely predicted by the second-order closure models. but the scalar field is less satisfactory, with the scalar fluctuation level underpredicted. Strong intermittency of the low-Reynolds-number flow field is suspected of these discrepancies. The trends in second- and third-order velocity-scalar correlations, which describe turbulent transport phenomena, are also predicted in general, with the cross-streamwise correlations better than the streamwise one. Buoyancy terms modeling the pressure-correlation are shown to improve the prediction slightly. The effects of equilibrium time-scale ratio and boundary condition are also discussed

Community involvement in the restoration of historic urban parks : with a specific focus on the Heritage Lottery Fund's Urban Parks Programme grant-aided park restoration projects.

Community involvement is nowadays commonly recognised as an integral part of any successful environmental planning, development and regeneration process. Focusing on a selection of park restoration projects grant-aided by the Heritage Lottery Fund (HLF) in 1997 under the Urban Parks Programme (UPP), this research aimed primarily to investigate the involvement of local communities in the process of regenerating run-down historic urban parks. The study adopted a triangulation methodology which combined both quantitative and qualitative research approaches and employed multiple data-collecting techniques including a postal questionnaire survey, semi-structured interviews, focus groups and on-site park user surveys. The results of the postal questionnaire survey reveal that park restoration partnerships between local authorities, private sector, voluntary organisations and local community-based groups can commonly be observed in many of the historic urban park restoration projects funded by the HLF under the UPP. Local authorities in general played the leading role in forming and running park restoration partnerships and they were the major contributors to the matched funding and the required technical support for the restoration projects. The involvement of friends groups and other local organisations in park restoration partnerships was relatively moderate, but the case studies of this research demonstrate that friends groups and other local organisations can have a more substantial influence on the overall development of the restoration project when the park restoration partnership is formally established. The study has found that local communities have been extensively involved in the restoration process of historic urban parks. The two most significant objectives of engaging local communities in regenerating run-down historic urban parks are to generate a sense of ownership of the restoration project and its outcome and to better reflect local needs. Local communities tend to be more involved at early stages of the restoration project than at later stages. The methods that have been commonly used to involve local communities are mainly for information giving and consultation. The seven in-depth case studies reveal that 'Friends of Parks' groups are in general the focus of community involvement in the UPP funded park restoration projects. 'Friends of Parks' groups can act as pressure groups, guardians and/or supporters of the park and to be the local community's voice. They can make considerable contributions to the regeneration of their local parks, mainly in the areas of publicity, park events and activities, fund raising, public consultation, project monitoring, involving school children, and the ongoing management of the restored park. The most important contributory factor to effective community involvement is a good relationship between the local authority and the 'Friends of Parks' groups, which can be achieved mainly by establishing friends groups' trust in the local authority's commitment to caring for urban parks and taking on board the friends groups' views and concerns. Project managers and other practitioners engaged in involving local communities in park restoration processes as well as executive members of 'Friends of Parks' groups are all required to have good communication skills in order to achieve effective community involvement

Rapid mix concepts for low emission combustors in gas turbine engines

NASA LeRC has identified the Rich burn/Quick mix/Lean burn (RQL) combustor as a potential gas turbine combustor concept to reduce NOx emissions in High Speed Civil Transport (HSCT) aircraft. To demonstrate reduced NOx levels, NASA LeRC soon will test a flametube version of an RQL combustor. The critical technology needed for the RQL combustor is a method of quickly mixing combustion air with rich burn gases. Two concepts were proposed to enhance jet mixing in a circular cross-section: the Asymmetric Jet Penetration (AJP) concept; and the Lobed Mixer (LM) concept. In Phase 1, two preliminary configurations of the AJP concept were compared with a conventional 12-jet radial-inflow slot design. The configurations were screened using an advanced 3-D Computational Fluid Dynamics (CFD) code named REFLEQS. Both non-reacting and reacting analyses were performed. For an objective comparison, the conventional design was optimized by parametric variation of the jet-to-mainstream momentum flux (J) ratio. The optimum J was then employed in the AJP simulations. Results showed that the three-jet AJP configuration was superior in overall mixedness compared to the conventional design. However, in regards to NOx emissions, the AJP configuration was inferior. The higher emission level for AJP was caused by a single hot spot located in the wake of the central jet as it entered the combustor. Ways of maintaining good mixedness while eliminating the hot spot were identified for Phase 2 study. Overall, Phase 1 showed the viability of using CFD analyses to evaluate quick-mix concepts. A high probability exists that advancing mixing concepts will reduce NOx emissions in RQL combustors, and should be explored in Phase 2, by parallel numerical and experimental work

Vibration characteristics and modal analysis of a grinding machine

The machine industry has undergone several developments in the past years, and reducing the cost and time required for machine designing is important. In this study, the vibration characteristics of a precision grinding machine were obtained through experimental modal analysis and finite element analysis. The experimental modal analysis employed single point excitation, and the equipment used to determine the frequency response of the grinding machine comprised a hammer, an accelerometer, and a spectrum analyzer. In addition, the resonance frequency, damping factor, and modal shape of the grinding machine were determined. The natural frequency, modal shape, and interface stiffness were determined through finite element analysis. Finally, the theoretical model and the experimental modal analysis models were compared, and get closer to the actual situation of a model to conduct several times analysis. Thus, this paper presents a reliable and convenient method to study the characteristics of machine tools; this method can reduce unnecessary costs and find structural weaknesses in machine designs for improvement

Distinct functional defect of three novel Brugada syndrome related cardiac sodium channel mutations

The Brugada syndrome is characterized by ST segment elevation in the right precodial leads V1-V3 on surface ECG accompanied by episodes of ventricular fibrillation causing syncope or even sudden death. The molecular and cellular mechanisms that lead to Brugada syndrome are not yet completely understood. However, SCN5A is the most well known responsible gene that causes Brugada syndrome. Until now, more than a hundred mutations in SCN5A responsible for Brugada syndrome have been described. Functional studies of some of the mutations have been performed and show that a reduction of human cardiac sodium current accounts for the pathogenesis of Brugada syndrome. Here we reported three novel SCN5A mutations identified in patients with Brugada syndrome in Taiwan (p.I848fs, p.R965C, and p.1876insM). Their electrophysiological properties were altered by patch clamp analysis. The p.I848fs mutant generated no sodium current. The p.R965C and p.1876insM mutants produced channels with steady state inactivation shifted to a more negative potential (9.4 mV and 8.5 mV respectively), and slower recovery from inactivation. Besides, the steady state activation of p.1876insM was altered and was shifted to a more positive potential (7.69 mV). In conclusion, the SCN5A channel defect related to Brugada syndrome might be diverse but all resulted in a decrease of sodium current

A Shallow Ritz Method for Elliptic Problems with Singular Sources

In this paper, a shallow Ritz-type neural network for solving elliptic equations with delta function singular sources on an interface is developed. There are three novel features in the present work; namely, (i) the delta function singularity is naturally removed, (ii) level set function is introduced as a feature input, (iii) it is completely shallow, comprising only one hidden layer. We first introduce the energy functional of the problem and then transform the contribution of singular sources to a regular surface integral along the interface. In such a way, the delta function singularity can be naturally removed without introducing a discrete one that is commonly used in traditional regularization methods, such as the well-known immersed boundary method. The original problem is then reformulated as a minimization problem. We propose a shallow Ritz-type neural network with one hidden layer to approximate the global minimizer of the energy functional. As a result, the network is trained by minimizing the loss function that is a discrete version of the energy. In addition, we include the level set function of the interface as a feature input of the network and find that it significantly improves the training efficiency and accuracy. We perform a series of numerical tests to show the accuracy of the present method and its capability for problems in irregular domains and higher dimensions

Changes in endotracheal tube cuff pressure during laparoscopic surgery in head-up or head-down position

BACKGROUND: The abdominal insufflation and surgical positioning in the laparoscopic surgery have been reported to result in an increase of airway pressure. However, associated effects on changes of endotracheal tube cuff pressure are not well established. METHODS: 70 patients undergoing elective laparoscopic colorectal tumor resection (head-down position, n = 38) and laparoscopic cholecystecomy (head-up position, n = 32) were enrolled and were compared to 15 patients undergoing elective open abdominal surgery. Changes of cuff and airway pressures before and after abdominal insufflation in supine position and after head-down or head-up positioning were analysed and compared. RESULTS: There was no significant cuff and airway pressure changes during the first fifteen minutes in open abdominal surgery. After insufflation, the cuff pressure increased from 26 ± 3 to 32 ± 6 and 27 ± 3 to 33 ± 5 cmH(2)O in patients receiving laparoscopic cholecystecomy and laparoscopic colorectal tumor resection respectively (both p < 0.001). The head-down tilt further increased cuff pressure from 33 ± 5 to 35 ± 5 cmH(2)O (p < 0.001). There six patients undergoing colorectal tumor resection (18.8%) and eight patients undergoing cholecystecomy (21.1%) had a total increase of cuff pressure more than 10 cm H(2)O (18.8%). There was no significant correlation between increase of cuff pressure and either the patient's body mass index or the common range of intra-abdominal pressure (10-15 mmHg) used in laparoscopic surgery. CONCLUSIONS: An increase of endotracheal tube cuff pressure may occur during laparoscopic surgery especially in the head-down position