Failure analysis of a Stirling engine heat pipe

Failure analysis was conducted on a heat pipe from a Stirling Engine test rig which was designed to operate at 1073 K. Premature failure had occurred due to localized overheating at the leading edge of the evaporator fin. It was found that a crack had allowed air to enter the fin and react with the sodium coolant. The origin of the crack was found to be located at the inner surface of the Inconel 600 fin where severe intergranular corrosion had taken place

Risk factors for hospitalization of children with diarrhea in Shahrekord, Iran

Background: Diarrheal infections are responsible for over a quarter of all childhood mortality worldwide. The present study was performed to establish risk factors for hospitalization of children with diarrhea in Shahrekord, Iran. Materials and methods: For this case-control study, cases were selected through children hospitalized due to acute diarrhea lasting less than 14 days and controls were compromised of children with a clinical diagnosis of acute diarrhea lasting for less than 14 days who did not require hospitalization. Controls were selected from out-patient department (OPD) or 3 primary health care centers. Results: The study population included 259 hospitalized children (cases), 245 OPD and 245 primary health centres controls. In total, bloody diarrhea, dehydration, breastfeeding for ≤6 months, history of hospitalization in the previous year, lack of access to safe water, keeping animals at home and the presence of watery stool were associated with an increased risk of hospitalization during univariate analysis. However, multivariate analysis revealed that bloody diarrhea, watery stool, vomiting, use of unsafe water, prior hospitalization, and the presence of rotavirus or salmonella in the stool were independent factors increasing the risk of hospitalization. Conclusion: Our results indicate that improving environmental sanitation, socio-economic status and establishing training programs for parents can reduce risk of hospitalization due to diarrhea in children

Domination Number of the Non-commuting Graph of Finite Groups

Let G be a non-abelian group. The non-commuting graph of group G, shown by ΓG, is a graph with the vertex set G \ Z(G), where Z(G) is the center of group G. Also two distinct vertices of a and b are adjacent whenever ab ≠ ba. A set S ⊆ V(Γ) of vertices in a graph Γ is a dominating set if every vertex v ∈ V(Γ) is an element of S or adjacent to an element of S. The domination number of a graph Γ denoted by γ(Γ), is the minimum size of a dominating set of Γ. </p><p>Here, we study some properties of the non-commuting graph of some finite groups. In this paper, we show that \gamma(\Gamma_G)<\frac{|G|-|Z(G)|}{2}. Also we charactrize all of groups G of order n with t = ∣Z(G)∣, in which $\gamma(\Gamma_{G})+\gamma(\overline{\Gamma}_{G})\in \{n-t+1,n-t,n-t-1,n-t-2\}.

Modeling of micro flows using perturbation method

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.A new method for modeling micro flows is presented in this research. The basis of this method is the development of governing continuum equations on fluid dynamics using perturbation expansion of the velocity, pressure, density and temperature fields in dependence of Knudsen number. In the present work, we use three-term perturbation expansions and reach three order of equations O(1), O(Kn), O(Kn2). Required boundary conditions (BC) for solving each order of these equations are obtained by substitution of the perturbation expansions into the general boundary conditions for the velocity slip and temperature jump. This set of equations is discretized in two-dimensional state on a staggered grid using the finite volume method. A three-part computer program has been produced for solving the set of discretized equations. Each part of this code, solve one order of the equations with the SIMPLE algorithm. Incompressible slip micro Poiseuille and micro Couette flows are solved either analytically or numerically using the perturbation method (PM). Good agreement is found between analytical and numerical results in the low Knudsen numbers, whereas numerical results deviate from analytical results by increasing the Knudsen number. The results of perturbation method are also compared with the results obtained from different slip models

In-vitro application of pentoxifylline preserved ultrastructure of spermatozoa after vitrification in asthenozoospermic patients

Abstract PURPOSE: To evaluate the effect of in vitro application of pentoxifylline (PX) on sperm parameters and ultrastructure after vitrification in asthenozoospermic patients. MATERIALS AND METHODS: A total of 30 asthenozoospermic semen samples (aged 25-45 years) were divided into four groups before vitrification, after vitrification, control (without PX) and experimental (with PX). In experimental group, each sample was exposed for 30 min to 3.6mmol/l PX and the control group without any treatment apposing in 370C for 30 min. After incubation, the samples were washed and analyzed again. Vitrification was done according to straw method. Eosin-nigrosin and Papanicolaou staining were applied for assessment of sperm viability and morphology, respectively. The samples without PX and post treatment with PX were assessed by transmission electron microscopy (TEM). RESULTS: A significant decrease in sperm motility (P ≤ .001), morphology (11.47 ± 2.9 versus 6.73 ± 2.01) and viability (73.37 ± 6.26 versus 54.67 ± 6.73) was observed post vitrification, but sperm motility (19.85 ± 4.75 versus 32.07 ± 5.58, P ≤ .001) was increased significantly following application of PX. This drug had no significant (P >.05) detrimental neither negative effect on ultrastructure acrosome, plasma membrane and coiled tail statues of spermatozoa. CONCLUSION: Vitrification had detrimental effects on sperm parameters, but PX reversed detrimental effects on sperm motility. However, PX had no alteration on ultrastructure morphology of human spermatozoa after vitrification

Complete Semantics to empower Touristic Service Providers

The tourism industry has a significant impact on the world's economy, contributes 10.2% of the world's gross domestic product in 2016. It becomes a very competitive industry, where having a strong online presence is an essential aspect for business success. To achieve this goal, the proper usage of latest Web technologies, particularly schema.org annotations is crucial. In this paper, we present our effort to improve the online visibility of touristic service providers in the region of Tyrol, Austria, by creating and deploying a substantial amount of semantic annotations according to schema.org, a widely used vocabulary for structured data on the Web. We started our work from Tourismusverband (TVB) Mayrhofen-Hippach and all touristic service providers in the Mayrhofen-Hippach region and applied the same approach to other TVBs and regions, as well as other use cases. The rationale for doing this is straightforward. Having schema.org annotations enables search engines to understand the content better, and provide better results for end users, as well as enables various intelligent applications to utilize them. As a direct consequence, the region of Tyrol and its touristic service increase their online visibility and decrease the dependency on intermediaries, i.e. Online Travel Agency (OTA).Comment: 18 pages, 6 figure

Urban heat mitigation by green and blue infrastructure: drivers, effectiveness, and future needs

The combination of urbanization and global warming leads to urban overheating and compounds the frequency and intensity of extreme heat events due to climate change. Yet, the risk of urban overheating can be mitigated by urban green-blue-grey infrastructure (GBGI), such as parks, wetlands, and engineered greening, which have the potential to effectively reduce summer air temperatures. Despite many reviews, the evidence bases on quantified GBGI cooling benefits remains partial and the practical recommendations for implementation are unclear. This systematic literature review synthesizes the evidence base for heat mitigation and related co-benefits, identifies knowledge gaps, and proposes recommendations for their implementation to maximize their benefits. After screening 27,486 papers, 202 were reviewed, based on 51 GBGI types categorized under 10 main divisions. Certain GBGI (green walls, parks, street trees) have been well researched for their urban cooling capabilities. However, several other GBGI have received negligible (zoological garden, golf course, estuary) or minimal (private garden, allotment) attention. The most efficient air cooling was observed in botanical gardens (5.0 ± 3.5°C), wetlands (4.9 ± 3.2°C), green walls (4.1 ± 4.2°C), street trees (3.8 ± 3.1°C), and vegetated balconies (3.8 ± 2.7°C). Under changing climate conditions (2070–2100) with consideration of RCP8.5, there is a shift in climate subtypes, either within the same climate zone (e.g., Dfa to Dfb and Cfb to Cfa) or across other climate zones (e.g., Dfb [continental warm-summer humid] to BSk [dry, cold semi-arid] and Cwa [temperate] to Am [tropical]). These shifts may result in lower efficiency for the current GBGI in the future. Given the importance of multiple services, it is crucial to balance their functionality, cooling performance, and other related co-benefits when planning for the future GBGI. This global GBGI heat mitigation inventory can assist policymakers and urban planners in prioritizing effective interventions to reduce the risk of urban overheating, filling research gaps, and promoting community resilience

Assessing Service Quality at Optical Centers in Palestine Using SERVQUAL: Measuring Ambiguity

The main purpose of this article is to employ the SERVQUAL model to assess customers’ perceptions and expectations of service quality in the optical centers in the West Bank of Palestine, and to examine the impact of this service quality on their satisfaction. A focused critical review of the service quality literature was undertaken. Data was collected from a convenient and purposeful sample of 251 customers of optical centers in the West Bank via personally administered and online questionnaires. Data was analyzed, with the aid of SPSS, using descriptive and inferential statistics, including the Mann-Whitney test, the Kruskal-Wallis test, regression analysis, and the Wilcoxon signed-rank test. The findings indicate that SERVQUAL proved to be a good tool for the purpose of assessing the gaps between customers’ expectations and perceptions of the service quality of optical centers in the Palestinian context. The findings also confirmed that customers had higher service quality expectations than perceptions in all the five dimensions of SERVQUAL. The developed regression analysis model shows that tangibles, reliability, assurance, and empathy had a significant statistical impact on customers’ satisfaction. No studies, to the best knowledge of the authors, were conducted on customers’ perceptions and expectations of service quality in the optical centers in the Palestinian context. Limitations of the study’s methodology and findings were discussed and avenues for further research suggested. The findings of this study could be valuable to interested parties including optometry regulators and managers of optical centers

Using continuous wavelet transform of generalized flexibility matrix in damage identification

Generalized flexibility matrix method has recently been introduced for identifying damages with the aim of overcoming some shortcomings of the approaches based on flexibility matrix. Researchers that use flexibility matrix to detect damages in structures face truncation errors ensue from cut off higher-order mode shapes, which are difficult to measure in practice. In this paper, a new procedure is presented to detect the damage site in a beam-type structure, where generalized flexibility matrix in conjunction with continuous wavelet transform (CWT) is utilized. Since flaws and cracks cause changes in flexibility of a system, this characteristic can be used as a damage indicator. Gaussian wavelet transform with four vanishing moments as a signal processing method is implemented to find the irregularity in a vector obtained from generalized flexibility matrix which is considered as a sign of damage. This method does not need to have either prior knowledge about the intact structure or its finite element model. The proposed technique is evaluated by numerical and experimental case studies