scholarly journals Dynamic Models of Vibrating Rotor Stages

1966 ◽  
Author(s):  
Hans Stargardter
Keyword(s):  
Silicone Rubber ◽  
Dynamic Models ◽  
Visual Observation ◽  
Small Scale ◽  
Complex Shapes ◽  
Scale Models ◽  
Dynamic Stimulus ◽  
The Many ◽  
Dynamic Excitations ◽  
Integral Order

Fan and compressor stages of turbofan aircraft engines are subjected to dynamic excitations. Often these excitations are at frequencies equal to or multiples of the rotor speed. This form of dynamic stimulus is called per-revolution excitation or integral-order excitation. When the natural resonant frequency of a fan stage coincides with the frequency of the source, severe vibration usually results. For shrouded fan stages the natural frequency is that of a coupled dynamic system consisting of disk, blades, and shroud. A modeling technique is developed to study the vibration. Small scale models are cast of flexible silicone rubber, known as RTV. The rubber models rotate and are excited by air nozzles located at discrete circumferential positions. Visual observation of the standing-wave oscillation clearly shows the familiar relations of forced vibrations such as magnification factor, phase shift, and the effects of damping. RTV silicone rubber is easily cast into complex shapes. This allows rapid evaluation of the many resonant-response blade-disk shroud configurations including unsymmetrical designs that may be difficult to analyze with current computing techniques.

scholarly journals Modelling and Forecasting Domestic Tourism. Case Study from Armenia

2021 ◽  
Vol 5 (2) ◽  
pp. 96-110
Author(s):  
Karen Poghosyan ◽  
Gayane Tovmasyan
Keyword(s):  
Large Scale ◽  
Dynamic Models ◽  
Dynamic Modelling ◽  
Tourism Development ◽  
Point Of View ◽  
Sufficient Evidence ◽  
Small Scale ◽  
Scale Models ◽  
Domestic Tourism ◽  
Modelling And Forecasting

This paper summarizes the arguments and counterarguments within the scientific discussion on the issue of modelling and forecasting domestic tourism. During Covid-19 many countries tried to develop domestic tourism as an alternative to inbound tourism. In Armenia domestic tourism has grown recently, and in 2020 the decrease was 33% compared to last year. The main purpose of the research is to model and forecast domestic tourism growth in Armenia. Systematization of the literary sources and approaches for solving the problem indicates that many models and different variables are used to forecast tourism development. Methodological tools of the research methods were static and dynamic models, years of research were 2001-2020, quarterly data. The paper presents the results of an empirical analysis, which showed that with the static regression analysis a 1% change in GDP will lead to a change of 4.43% in the number of domestic tourists, a 1% change in the CPI will lead to a 14.55% change in the number of domestic tourists. For dynamic modelling we used 12 competing short-term forecasting models. Based on the recursive and rolling forecast simulation results we concluded that out-of-sample forecasts obtained by the small-scale models outperform forecasts obtained by the large-scale models at all forecast horizons. So, the forecasts of the domestic tourists’ growth obtained by small-scale models are more appropriate from the practical point of view. Then, in order to check whether the differences in forecasts obtained by the different models are statistically significant we applied Diebold-Mariano test. Based on the results of this test we concluded that there is not sufficient evidence to favor large-scale over small-scale models. This means that the forecast results obtained for domestic tourist growth by using the small scale models would not be statistically different from the results obtained by the large scale models. Based on the analysis, the forecasted values for domestic tourists for the future years were determined. The results of the research can be useful for state bodies, as well as private organizations, and for everybody who wants to model and forecast tourism development.

scholarly journals Cognitive map formation through haptic and visual exploration of tactile city-like maps

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Loes Ottink ◽  
Marit Hoogendonk ◽  
Christian F. Doeller ◽  
Thea M. Van der Geest ◽  
Richard J. A. Van Wezel
Keyword(s):  
Visual Information ◽  
Spatial Information ◽  
Cognitive Map ◽  
Visual Exploration ◽  
Distinct Advantage ◽  
Small Scale ◽  
Map Learning ◽  
Scale Models ◽  
Spatial Tasks ◽  
Tactile Maps

AbstractIn this study, we compared cognitive map formation of small-scale models of city-like environments presented in visual or tactile/haptic modalities. Previous research often addresses only a limited amount of cognitive map aspects. We wanted to combine several of these aspects to elucidate a more complete view. Therefore, we assessed different types of spatial information, and consider egocentric as well as allocentric perspectives. Furthermore, we compared haptic map learning with visual map learning. In total 18 sighted participants (9 in a haptic condition, 9 visuo-haptic) learned three tactile maps of city-like environments. The maps differed in complexity, and had five marked locations associated with unique items. Participants estimated distances between item pairs, rebuilt the map, recalled locations, and navigated two routes, after learning each map. All participants overall performed well on the spatial tasks. Interestingly, only on the complex maps, participants performed worse in the haptic condition than the visuo-haptic, suggesting no distinct advantage of vision on the simple map. These results support ideas of modality-independent representations of space. Although it is less clear on the more complex maps, our findings indicate that participants using only haptic or a combination of haptic and visual information both form a quite accurate cognitive map of a simple tactile city-like map.

scholarly journals Roughness Lengths for Momentum and Heat Derived from Outdoor Urban Scale Models

2007 ◽  
Vol 46 (7) ◽  
pp. 1067-1079 ◽  
Author(s):  
M. Kanda ◽  
M. Kanega ◽  
T. Kawai ◽  
R. Moriwaki ◽  
H. Sugawara
Keyword(s):  
Wind Direction ◽  
Roughness Length ◽  
Scale Dependence ◽  
Scale Model ◽  
Small Scale ◽  
Physical Scale ◽  
Scale Models ◽  
Roughness Lengths ◽  
Urban Sites ◽  
Obstacle Height

Abstract Urban climate experimental results from the Comprehensive Outdoor Scale Model (COSMO) were used to estimate roughness lengths for momentum and heat. Two different physical scale models were used to investigate the scale dependence of the roughness lengths; the large scale model included an aligned array of 1.5-m concrete cubes, and the small scale model had a geometrically similar array of 0.15-m concrete cubes. Only turbulent data from the unstable boundary layers were considered. The roughness length for momentum relative to the obstacle height was dependent on wind direction, but the scale dependence was not evident. Estimated values agreed well with a conventional morphometric relationship. The logarithm of the roughness length for heat relative to the obstacle height depended on the scale but was insensitive to wind direction. COSMO data were used successfully to regress a theoretical relationship between κB−1, the logarithmic ratio of roughness length for momentum to heat, and Re*, the roughness Reynolds number. Values of κB−1 associated with Re* for three different urban sites from previous field experiments were intercompared. A surprising finding was that, even though surface geometry differed from site to site, the regressed function agreed with data from the three urban sites as well as with the COSMO data. Field data showed that κB−1 values decreased as the areal fraction of vegetation increased. The observed dependency of the bulk transfer coefficient on atmospheric stability in the COSMO data could be reproduced using the regressed function of Re* and κB−1, together with a Monin–Obukhov similarity framework.

Fine-Scale Fire Spread in Pine Straw

Fire ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 69
Author(s):  
Daryn Sagel ◽  
Kevin Speer ◽  
Scott Pokswinski ◽  
Bryan Quaife
Keyword(s):  
Fire Spread ◽  
Small Scale ◽  
Natural Setting ◽  
Fine Scale ◽  
Prescribed Burn ◽  
Fire Dynamics ◽  
Rate Of Spread ◽  
Scale Models ◽  
Fire Front ◽  
Visible Images

Most wildland and prescribed fire spread occurs through ground fuels, and the rate of spread (RoS) in such environments is often summarized with empirical models that assume uniform environmental conditions and produce a unique RoS. On the other hand, representing the effects of local, small-scale variations of fuel and wind experienced in the field is challenging and, for landscape-scale models, impractical. Moreover, the level of uncertainty associated with characterizing RoS and flame dynamics in the presence of turbulent flow demonstrates the need for further understanding of fire dynamics at small scales in realistic settings. This work describes adapted computer vision techniques used to form fine-scale measurements of the spatially and temporally varying RoS in a natural setting. These algorithms are applied to infrared and visible images of a small-scale prescribed burn of a quasi-homogeneous pine needle bed under stationary wind conditions. A large number of distinct fire front displacements are then used statistically to analyze the fire spread. We find that the fine-scale forward RoS is characterized by an exponential distribution, suggesting a model for fire spread as a random process at this scale.

Conclusion: An Alternative Agriculture for Our Time

2016 ◽  
Author(s):  
Connor J. Fitzmaurice ◽  
Brian J. Gareau
Keyword(s):  
Food Production ◽  
Food System ◽  
Consumer Involvement ◽  
Small Scale ◽  
Local Agriculture ◽  
Shopping Experience ◽  
Alternative Markets ◽  
Small Scale Farmers ◽  
Full Force ◽  
The Many

Without abandoning the practical idea of farming as a business, the small-scale farmers in this book foster connections between consumer experiences and expectations and farming practices that support their visions of organic. They try to build new, alternative markets to challenge the watering down of “organic” that the full-force entrance of corporate market logics ushered in. However, there are limitations to how sustainable such farming operations can be without further changing the relationships the modern food system is based upon. This chapter begins by recognizing the many limitations of localism, including the potentially neoliberal aspects of such efforts. However, the neoliberal notion that individuals can and should bring forth their own interests and engage in political contestation could (paradoxically) be the very kernel that further popularizes small-scale food production networks that provide safer, more healthful food and a better sense of community than the isolating conventional shopping experience. Finally, the chapter considers how deepening consumer involvement in the process of agriculture, incorporating concerns about social justice into local food systems, and addressing the inefficiencies of decentralized food production could push local agriculture to be even more alternative.

scholarly journals Kelayakan Usaha Ayam Broiler (Studi pada Usaha Peternakan di Desa Cibinong)

2018 ◽  
Vol 33 (2) ◽  
pp. 96
Author(s):  
Elpawati Elpawati ◽  
Achmad Tjachja Nugraha ◽  
Ratu Shofiatina
Keyword(s):  
Small Scale ◽  
Selling Price ◽  
Poultry Production ◽  
Poultry Farm ◽  
Financial Feasibility ◽  
Positive Growth ◽  
Poultry Farms ◽  
Positive Growth Rate ◽  
Small Scale Farmers ◽  
The Many

<p>Indonesia poultry consumption has increased year by year, with the average positive growth rate of 4.6%. This situation can be a chance for both small and large scales of poultry farmers, considering that poultry consumption is increasing every year. The rate of poultry production in Gunung Sindur was correlated with the amount of the existing poultry farms. Romli Farm was a small scale poultry farm in Gunung Sindur, Bogor. This poultry farm, with no partnership, could independently survive amongst the many other existing farms. However, although the opportunities were wide open, this business was not always viable for the farmers because many of small-scale farmers could not be able either to increase the income or to carry on the business. This research aimed to study the income, financial feasibility (NPV, IRR, Net B/C Ratio, and PP), the BEP of Selling Price, and the BEP of Product in Romli Farm.</p>

Tearing Resistance of Advanced Double Hulls

1997 ◽  
Vol 41 (01) ◽  
pp. 69-80
Author(s):  
Mark D. Bracco ◽  
Tomasz Wierzbicki
Keyword(s):  
Steady State ◽  
Cutting Force ◽  
Average Error ◽  
Small Scale ◽  
Complex Deformation ◽  
Scale Models ◽  
State Force ◽  
Deformation Patterns ◽  
Double Hull ◽  
Tearing Resistance

This paper studies the cutting by a wedge of advanced double hull (ADH) small-scale models. A total of six cutting experiments were performed with six different wedge geometries. Complex deformation patterns observed in the damaged specimens were simplified to obtain a closed-form upper bound for the steady-state cutting force. The ADH steady-state cutting force solution varied from 6% above to 12% below the experimental mean steady-state force. The absolute average error is 5%.

scholarly journals Situated transformations of women and gender relations in small-scale fisheries and communities in a globalized world

2019 ◽  
Vol 18 (3) ◽  
pp. 241-248 ◽  
Author(s):  
Katia Frangoudes ◽  
Siri Gerrard ◽  
Danika Kleiber
Keyword(s):  
Gender Equity ◽  
Small Scale ◽  
Women And Gender ◽  
The Sustainable Development ◽  
Small Scale Fisheries ◽  
Individual Household ◽  
Development Goals ◽  
And Gender ◽  
The Many ◽  
Globalized World

AbstractThe need to uncover, interrogate, and integrate women’s contributions to fisheries in research and development has never been clearer. As coastal and fisheries management continues to look to the Sustainable Development Goals and the Voluntary Guidelines for Securing Sustainable Small-Scale Fisheries in the context of Food Security and Poverty Eradication, as frameworks and mandates, gender equity and equality have become a central concern. To fill the still existing gap of documentation and theoretical engagement, in this thematic collection, we gather together voices from researchers and practitioners from around the world, with one overarching common approach of using a gender lens to examine the relationship between humans and aquatic resources. Drawing on Donna Haraway’s classic feminist concept of situated knowledges, we examine the many and varied approaches researchers are using to engage with the intersection of gender and fisheries. Beginning and ending with two reviews that examine where gender and fisheries has come from, and where it is going, this thematic issue includes case studies from 10 countries, engaging in the topic at various scales (individual, household, national, institutional etc.), and using multiple methodological approaches. Taken together, these pieces explore the mechanism by which women’s contribution to fisheries are overlooked and provide direct evidence to contest the persistent invisibility of women in fishing, fisheries labor, and fisheries decision-making. Going beyond the evidence of women’s contributions, the authors go further to examine different coastal contexts, intersectional identities such as age, and explore gender transformative approaches to fisheries development.

Sign in / Sign up

Export Citation Format

Share Document