1,650 research outputs found

    Pure Steam Condensation Experiments on Nonisothermal Vertical Plates

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    Dissipation equals production in the log layer of wall-induced turbulence

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    Asymptotic analysis is presented of the energy balance equations derived from statistically averagedNavier-Stokes equations pertinent to wall-induced turbulence. Attention is focused on the inertialsublayer, the region outside the viscous sublayer, and the buffer layer where the log-law for meanflow holds. Production and dissipation of turbulence are shown to be equal with a relative error of order(x2 /L), where x2 is the distance from the wall and L is the external length (pipe radius, channelhalf-height, boundary layer thickness). Diffusion of pressure and kinetic energy together are only ofrelative magnitude order (x2 /L). Pressure gradient terms are shown to redistribute longitudinalturbulence production in equal portions dissipated in the three orthogonal directions

    Pauli graphs, Riemann hypothesis, Goldbach pairs

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    Let consider the Pauli group Pq=\mathcal{P}_q= with unitary quantum generators XX (shift) and ZZ (clock) acting on the vectors of the qq-dimensional Hilbert space via Xs>=s+1>X|s> =|s+1> and Zs>=ωss>Z|s> =\omega^s |s>, with ω=exp(2iπ/q)\omega=\exp(2i\pi/q). It has been found that the number of maximal mutually commuting sets within Pq\mathcal{P}_q is controlled by the Dedekind psi function ψ(q)=qpq(1+1p)\psi(q)=q \prod_{p|q}(1+\frac{1}{p}) (with pp a prime) \cite{Planat2011} and that there exists a specific inequality ψ(q)q>eγloglogq\frac{\psi (q)}{q}>e^{\gamma}\log \log q, involving the Euler constant γ0.577\gamma \sim 0.577, that is only satisfied at specific low dimensions qA={2,3,4,5,6,8,10,12,18,30}q \in \mathcal {A}=\{2,3,4,5,6,8,10,12,18,30\}. The set A\mathcal{A} is closely related to the set A{1,24}\mathcal{A} \cup \{1,24\} of integers that are totally Goldbach, i.e. that consist of all primes p2p2) is equivalent to Riemann hypothesis. Introducing the Hardy-Littlewood function R(q)=2C2pnp1p2R(q)=2 C_2 \prod_{p|n}\frac{p-1}{p-2} (with C20.660C_2 \sim 0.660 the twin prime constant), that is used for estimating the number g(q)R(q)qln2qg(q) \sim R(q) \frac{q}{\ln^2 q} of Goldbach pairs, one shows that the new inequality R(Nr)loglogNreγ\frac{R(N_r)}{\log \log N_r} \gtrapprox e^{\gamma} is also equivalent to Riemann hypothesis. In this paper, these number theoretical properties are discusssed in the context of the qudit commutation structure.Comment: 11 page

    Rheology Modifying Admixtures: The Key to Innovation in Concrete Technology – A General Overview and Implications for Africa

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    Innovative admixture technology has significantly widened up the range of possibilities of concrete engineers. For many decades the water to cement ratio (w/c) was the major influencing factor for the performance of concrete. Due to the need to adjust a consistency, which still allowed reasonable workability, the w/c was typically significantly higher than technologically reasonable. Rheology modifying admixtures support adjusting the concrete consistency largely independent of the w/c. It was only after the invention of the first superplasticizers that modern concrete technology significantly evolved in terms of flowability, strength, and durability, and only due to the steady evolution of the technology modern innovations, such as Self-Compacting Concrete, Ultra-High-Performance Concrete, or Engineered Cementitious Composites were made possible. Today’s superplasticizers are extremely versatile and can be adjusted to individual technological specifications. However, the other side of the coin of versatility is that cementitious systems incorporating superplasticizers have become more sensitive against environmental influences, such as the environmental temperature, which may cause unwanted effects or demand for supplementary admixture use such as stabilizing admixtures. Hence, concrete mixture composition with admixtures demands for a high level of expertise and often there is lack of awareness about the mode of operation of rheology modifying admixtures among concrete technologists. The paper gives a comprehensive overview about rheology modifying admixtures such as superplasticizers or stabilizing agents, and how they can be used depending upon the application in the most favourable way. Based on experiences with the sub-Saharan African concreting boundary conditions, which exhibit many challenges in terms of environmental boundary conditions and construction site logistics, conclusions are finally drawn, how admixtures can be used in the most beneficial way to improve the concrete casting situation

    Barriers to and facilitators for finding and keeping competitive employment:A focus group study on autistic adults with and without paid employment

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    PurposeThe aim of the study was to gain more insight into barriers to and facilitators for finding and keeping competitive employment for autistic adults. Research questions were: (1) What barriers and facilitators do autistic adults report in finding and keeping competitive employment?; and (2) What are differences and similarities between autistic adults with and without paid employment regarding barriers and facilitators for sustainable employment?MethodsEight focus groups were conducted (N = 64 autistic adults). Four groups included only participants without paid employment (N = 24), and four groups consisted exclusively of participants with current paid employment (including part-time, N = 40). All discussions were audiotaped and transcribed verbatim to enable inductive thematic content analysis. Data were analyzed using ATLAS.ti 9.ResultsTen themes and thirty-four subthemes were found. Many were interconnected. Themes facilitating sustainable employment included a positive workplace atmosphere, a supportive supervisor, being able to do work that aligns with interests and talents, favorable physical working conditions, coaching, higher self-insight, higher self-esteem, and proactivity. Most themes and subthemes emerged from both groups. Differences between the groups were that those with paid employment seemed to have experienced more friendly workplaces and supervisors, had received better coaching in finding and keeping employment, had higher self-insight and higher self-esteem, were more assertive and proactive.ConclusionsAs many (sub-)themes were interrelated, the results suggest that to improve work participation, particularly two key areas are promising: (1) to realize more friendly, well-being oriented and inclusive workplaces, and (2) to increase autistic adults’ self-insight into personal needs for positive wellbeing and self-knowledge regarding talents, wishes and well-being boundaries

    A retrospective analysis of the diagnostic performance of 11C-choline PET/CT for detection of hyperfunctioning parathyroid glands after prior negative or discordant imaging in primary hyperparathyroidism

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    BACKGROUND: Identifying the correct location of a parathyroid adenoma in patients with primary hyperparathyroidism (pHPT) is crucial as it can guide surgical treatment. This study aimed to determine the diagnostic performance of 11C-choline PET/CT in patients with pHPT as a next in-line scan after primary negative or discordant first-line imaging. METHODS: This was a retrospective single-center cohort study. All patients with pHPT that were scanned utilizing 11C-choline PET/CT, after prior negative or discordant imaging, between 2015 and 2019 and who subsequently underwent parathyroid surgery were included. The results of the 11C-choline PET/CT were evaluated lesion-based, with surgical exploration and histopathological examination as the gold standard. RESULTS: In total, 36 patients were included of which three patients were known to have Multiple Endocrine Neoplasia (MEN) syndrome. In these 36 patients, 40 lesions were identified on 11C-choline PET/CT and 37 parathyroid lesions were surgically removed. In 34/36 (94%) patients a focused parathyroidectomy was performed, in one patient a cervical exploration due to an ectopically identified adenoma, and in one patient a bilateral exploration was performed because of a double adenoma. Overall, per-lesion sensitivity of 11C-choline PET/CT was 97%, the positive predictive value was 95% and the accuracy was 94% for all parathyroid lesions. CONCLUSIONS: In patients with pHPT and prior negative or discordant first-line imaging results, pathological parathyroid glands can be localized by 11C-choline PET/CT with high sensitivity and accuracy

    Thermal treatment on MSWI bottom ash fines, in:

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    Abstract The municipal solid waste incineration (MSWI
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