Some dynamics of acoustic oscillations with nonlinear combustion and noise

The results given in this paper constitute a continuation of progress with nonlinear analysis of coherent oscillations in combustion chambers. We are currently focusing attention on two general problems of nonlinear behavior important to practical applications: the conditions under which a linearly unstable system will execute stable periodic limit cycles; and the conditions under which a linearly stable system is unstable to a sufficiently large disturbance. The first of these is often called 'soft' excitation, or supercritical bifurcation; the second is called 'hard' excitation, 'triggering,' or subcritical bifurcation and is the focus of this paper. Previous works extending over more than a decade have established beyond serious doubt (although no formal proof exists) that nonlinear gasdynamics alone does not contain subcritical bifurcations. The present work has shown that nonlinear combustion alone also does not contain subcritical bifurcations, but the combination of nonlinear gasdynamics and combustion does. Some examples are given for simple models of nonlinear combustion of a solid propellant but the broad conclusion just mentioned is valid for any combustion system. Although flows in combustors contain considerable noise, arising from several kinds of sources, there is sound basis for treating organized oscillations as distinct motions. That has been an essential assumption incorporated in virtually all treatments of combustion instabilities. However, certain characteristics of the organized or deterministic motions seem to have the nature of stochastic processes. For example, the amplitudes in limit cycles always exhibit a random character and even the occurrence of instabilities seems occasionally to possess some statistical features. Analysis of nonlinear coherent motions in the presence of stochastic sources is therefore an important part of the theory. We report here a few results of power spectral densities of acoustic amplitudes in the presence of a subcritical bifurcation associated with nonlinear combustion and gasdynamics

Structure and clumping in the fast wind of NGC6543

Far-UV spectroscopy from the FUSE satellite is analysed to uniquely probe spatial structure and clumping in the fast wind of the central star of the H-rich planetary nebula NGC6543 (HD164963). Time-series data of the unsaturated PV 1118, 1128 resonance line P Cygni profiles provide a very sensitive diagnostic of variable wind conditions in the outflow. We report on the discovery of episodic and recurrent optical depth enhancements in the PV absorption troughs, with some evidence for a 0.17-day modulation time-scale. SEI line-synthesis modelling is used to derive physical properties, including the optical depth evolution of individual `events'. The characteristics of these features are essentially identical to the `discrete absorption components' (DACs) commonly seen in the UV lines of massive OB stars. We have also employed the unified model atmosphere code CMFGEN to explore spectroscopic signatures of clumping, and report in particular on the clear sensitivity of the PV lines to the clump volume filling factor. The results presented here have implications for the downward revision of mass-loss rates in PN central stars. We conclude that the temporal structures seen in the PV lines of NGC6543 likely have a physical origin that is similar to that operating in massive, luminous stars, and may be related to near-surface perturbations caused by stellar pulsation and/or magnetic fields.Comment: 11 pages, 11 figures. Accepted for publication in MNRA

Pengaruh Latihan Fisik Terhadap Peningkatan Vo2Max Pemain Futsal STKIP BBG Banda Aceh

This study aims to determine the physical effect of Vmax in futsal athletes, with a total sample of 8 people. The sampling technique was done by total sampling. The data collection techniques used in this study were as follows: (1) training was carried out by means of total sampling. conduct an effective program as far as 2 km to 5 km with the initial test using vo2max on the futsal athletes of the Bina Bangsa College of Teacher Training and Education, Getsempena Banda Aceh. The results of the research obtained are that there is a significant effect of physical exercise on vo2max in the futsal athletes of the Teacher Training College And Education Science Bina Bangsa Getsempena Banda Aceh with an average value. The results of the above analysis showed that the T-count value of Vo2 Max to Vo2 Max was 3.33, while the T-table with degrees of freedom was 8-2 (dk = 6) at the level of the significance of α = 0.05 is 1.943. This means that the T-count value is greater than the T-table value. Thus, it can be concluded that there is a significant influence between Vo2Max and Vo2 Max on Futsal Players at the Getsempena National Development School, Banda Aceh.  Penelitian ini bertujuan untuk mengetahui pengaruh fisik terhadap vo2max pada atlit futsal yang berjumlah samplenya adalah 8 orang .Tehnik pengambilan sample di lakukan dengan cara total sampling.tehnik pengumpulan data yang di gunakan dalam penelitian ini adalah sebagai berikut :(1) latihan di lakukan dengan cara melakukan  program yang evektif sejauh 2 km sampai dengan 5 km dengan tes awalannnya menggunakan vo2max pada atlit futsal Sekolah Tinggi Keguruan Dan Ilmu Pendidikan Bina Bangsa Getsempena Banda Aceh.Hasil penelitian yang di proleh adalah terdapat pengaruh signifikan latihan fisik terhadap vo2max pada atlit futsal Sekolah Tinggi Keguruan Dan Ilmu Pendidikan Bina Bangsa Getsempena Banda Aceh  dengan nilai rata-rata Hasil analisis diatas, diperoleh nilai T-hitung dari  Vo2 Max  terhadap  Vo2 Max  sebesar 3,33, sedangkan T-tabel dengan derajat kebebasan 8-2 (dk =6) pada taraf signifikasi α = 0,05 adalah sebesar 1,943. Hal ini berati nilai T-hitung lebih besar dari nilai T-tabel. Dengan demikian dapat disimpulkan bahwa  terdapat Pengaruh yang signifikan antara Vo2Max  terhadap Vo2 Max  pada Pemain Futsal  Sekolah Tinngi Keguruan Dan Ilmu Pendidikaan  Bina Bangsa Getsempena Banda Aceh

Greenhouse gas emissions from non-recyclable residual household waste within domestic wheeled bins

The evolution of greenhouse gases (GHGs) from waste treatment processes (e.g. landfill & composting) are well documented (Chen and Lin, 2008), frequently quantified (Lou and Nair, 2009) and currently represented within climate change models (Ciais et al., 2013). Conversely, the understanding of GHG emissions from household waste (pre-collection) is largely unknown and confined to composting studies (e.g. Andersen et al., 2010), or calculating the calorific value/elemental content (Komilis et al., 2012) and biological methane potential (Alibardi and Cossu, 2015) of municipal solid waste. Generating a better understanding of GHG fluxes from non-recycled residual household waste before collection may help to further refine climate models and inform policy makers regarding the best collection strategy to mitigate GHG emissions

Strengthening community roles in aquatic resource governance in Uganda

Lake Victoria fisheries face severe environmental stresses. Stocks are declining in a context of increasing population and growing demand for the lake’s resources. Rising competition between users is putting conservation goals and rural livelihoods at risk. While Uganda’s co-management policy framework is well-developed, key resources for implementation are lacking, enforcement is poor, and the relations between stakeholders are unequal. Poor rural resource users face significant challenges to effectively participate in fisheries decision-making. This case study demonstrates the progress that can be made using a collaborative approach to catalyze community-led actions linking public health, sanitation and environmental conservation in difficult circumstances, even over a relatively short time period. Multistakeholder dialogue can bring to light the sources of conflict, pinpoint governance challenges, and identify opportunities for institutional collaboration to address community needs. At the same time, the process can help build trust, confidence in collective action and public accountability

Components of impactful dementia training for general hospital staff: a collective case study

Background and objectives: People with dementia occupy around one quarter of general hospital beds, with concerns consistently raised about care quality. Improving workforce knowledge, skills and attitudes is a mechanism for addressing this. However little is known about effective ways of training healthcare staff about dementia. This study aimed to understand models of dementia training most likely to lead to improved practice and better care experiences for people with dementia, and to understand barriers and facilitators to implementation. Method: A collective case study was conducted in three National Health Service Acute Hospital Trusts in England. Multiple data sources were used including interviews with training leads/facilitators, ward managers and staff who had attended training; satisfaction surveys with patients with dementia and/or carers; and observations of care using Dementia Care Mapping. Results: Interactive face-to-face training designed for general hospital staff was valued. Simulation and experiential learning methods were felt to be beneficial by some staff and stressful and distressing by others. Skilled delivery by an experienced and enthusiastic facilitator was identified as important. Staff identified learning and practice changes made following their training. However, observations revealed not all staff had the knowledge, attitudes and skills needed to deliver good care. Patient and carer satisfaction with care was mixed. A major barrier to training implementation was lack of resources. Supportive managers, organisational culture and strong leadership were key facilitators. Conclusion: Dementia training can lead to improved care practices. There are a range of key barriers and facilitators to implementation that must be considered

Refinement of atomic models in high resolution EM reconstructions using Flex-EM and local assessment

As the resolutions of Three Dimensional Electron Microscopic reconstructions of biological macromolecules are being improved, there is a need for better fitting and refinement methods at high resolutions and robust approaches for model assessment. Flex-EM/MODELLER has been used for flexible fitting of atomic models in intermediate-to-low resolution density maps of different biological systems. Here, we demonstrate the suitability of the method to successfully refine structures at higher resolutions (2.5–4.5 Å) using both simulated and experimental data, including a newly processed map of Apo-GroEL. A hierarchical refinement protocol was adopted where the rigid body definitions are relaxed and atom displacement steps are reduced progressively at successive stages of refinement. For the assessment of local fit, we used the SMOC (segment-based Manders’ overlap coefficient) score, while the model quality was checked using the Qmean score. Comparison of SMOC profiles at different stages of refinement helped in detecting regions that are poorly fitted. We also show how initial model errors can have significant impact on the goodness-of-fit. Finally, we discuss the implementation of Flex-EM in the CCP-EM software suite

Fatigue reduces the complexity of knee extensor torque during fatiguing sustained isometric contractions

The temporal structure, or complexity, of muscle torque output reflects the adaptability of motor control to changes in task demands. This complexity is reduced by neuromuscular fatigue during intermittent isometric contractions. We tested the hypothesis that sustained fatiguing isometric contractions would result in a similar loss of complexity. To that end, nine healthy participants performed, on separate days, sustained isometric contractions of the knee extensors at 20% MVC to task failure and at 100% MVC for 60 s. Torque and surface EMG signals were sampled continuously. Complexity and fractal scaling were quantified by calculating approximate entropy (ApEn) and the detrended fluctuation analysis (DFA) α scaling exponent. Global, central and peripheral fatigue were quantified using maximal voluntary contractions (MVCs) with femoral nerve stimulation. Fatigue reduced the complexity of both submaximal (ApEn from 1.02 ± 0.06 to 0.41 ± 0.04, P < 0.05) and maximal contractions (ApEn from 0.34 ± 0.05 to 0.26 ± 0.04, P < 0.05; DFA α from 1.41 ± 0.04 to 1.52 ± 0.03, P < 0.05). The losses of complexity were accompanied by significant global, central and peripheral fatigue (all P < 0.05). These results demonstrate that a fatigue-induced loss of torque complexity is evident not only during fatiguing intermittent isometric contractions, but also during sustained fatiguing contractions