scholarly journals The Effects of Initial Rise and Axial Loads on MEMS Arches

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
S. A. Tella ◽  
A. Z. Hajjaj ◽  
M. I. Younis
Keyword(s):  
Axial Load ◽  
Eigenvalue Problems ◽  
Recent Experimental Data ◽  
Axial Loads ◽  
Resonant Frequencies ◽  
The Past ◽  
Initial Rise ◽  
Resonance Frequencies ◽  
Initial Decrease

Arch microbeams have been utilized and proposed for many uses over the past few years due to their large tunability and bistability. However, recent experimental data have shown different mechanical behaviors of arches when subjected to axial loads, i.e., their stiffness may increase or decrease with applied axial loads. This paper aims to investigate in depth, the influence of the competing effects of initial rise and axial loads on the mechanical behavior of micromachined arches; mainly their static deflection and resonant frequencies. Based on analytical solutions, the static response and eigenvalue problems are analyzed for various values of initial rises and axial loads. Universal curves showing the variation of the first three resonance frequencies of the arch are generated for various values of initial rise under both tensile and compressive axial loads. This study shows that increasing the tensile or compressive axial loads for different values of initial rise may lead to either increase in the stiffness of the beam or initial decrease in the stiffness, which later increases as the axial load is increased depending on the dominant effect of the initial rise of the arch and the axial load. The obtained universal curves represent useful design tools to predict the tunability of arches under axial loads for various values of initial rises. The use of the universal curves is demonstrated with an experimental case study. Analytical formulation is developed to predict the point of minimum where the trend of the resonance frequency versus axial loads changes qualitatively due to the competing effects of axial loads and initial curvature.

scholarly journals Statics and Dynamics of V-shaped Micro-beams Under Axial Forces

2021 ◽  
Author(s):  
Hassen Ouakad ◽  
Nouha Alcheikh ◽  
Sofiane Ben Mbarek ◽  
Rodrigo Rocha ◽  
Mohammad Younis
Keyword(s):  
High Performance ◽  
Axial Loads ◽  
Electrostatically Actuated ◽  
High Tunability ◽  
Axial Forces ◽  
Initial Rise ◽  
Statics And Dynamics ◽  
Static Equation ◽  
Dc Bias

Abstract We present an investigation into the static and dynamic behaviors of electrostatically actuated in-plane micro-electro-mechanical V-shaped micro-beam under axial loads. The micro-beams are actuated with two separate electrodes of uniform air-gap across their length. The effects of the initial rise and DC bias voltage are examined while varying the axial loads ranging from compressive to tensile. The numerical analysis is based on a nonlinear equation of motion of a shallow V-shaped micro-beam. The static equation is solved using a reduced-order model based on the Galerkin procedure. Then, the eigenvalue problem of the structure is solved for various equilibrium positions. The analytical model is validated by comparing to an experimental case study. The results show rich and diverse static and dynamic behavior. It is shown that the micro-beam may exhibit only pull-in or snap-through and pull-in instabilities. Various multi-state and hysterics behaviors are demonstrated when varying the actuation forces and the initial rise. High tunability is demonstrated when varying the axial and DC loads for the first two symmetric vibration modes. Such rich behavior can be very useful for high performance micro-scale applications designs.

Improving the Performance of a Piezoelectric Energy Harvester Using a Tip Spring-Mass System

2012 ◽  
Author(s):  
Yang Zhu ◽  
Oumar Barry ◽  
Weijiun Su ◽  
Jean Zu
Keyword(s):  
Resonance Frequency ◽  
Piezoelectric Materials ◽  
Low Frequency ◽  
Ambient Vibration ◽  
Mass System ◽  
Resonant Frequencies ◽  
Energy Harvesters ◽  
The Past ◽  
Piezoelectric Energy

Vibration-based energy harvesting using piezoelectric materials has gained considerable attention over the past decade. Currently, most piezoelectric energy harvesters (PEHs) are single resonance frequency based. The performance of a single-resonance PEH is often limited to only one resonance frequency. This paper discusses the possibility of improving the performance of a bimorph PEH by tuning the PEH using a spring-mass system attached to the bimorph’s free end. Through adding the spring-mass system, the PEH’s resonance frequency can be tuned to match the ambient vibration frequency, and its voltage/power-generating capability can be improved. An electromechanical model of the PEH is derived based on the Lagrange multiplier method. The model is then used in a harmonic base excitation case study, and the coupled electromechanical outputs are discussed. Simulation results show that the spring-mass attachment can create two resonant frequencies, making the PEH capable of working efficiently at two different frequencies in a low-frequency level. It is also shown that by properly selecting the spring stiffness and the mass, the voltage and power output of the PEH can be greatly increased as compared to a single bimorph without the spring-mass system.

From hard to soft: theory and Neolithic studies in Scotland

2011 ◽  
Vol 33 (1-2) ◽  
pp. 7-19
Author(s):  
Kenneth Brophy
Keyword(s):  
The Past

The Scottish Theoretical Archaeology Group (STAG) conference organisers expressed some doubts about how far theory has changed, and impacted, archaeological establishment and academia in Scotland. In this paper, I will argue that Scotland is certainly not isolated in a theoretical sense, although in the past, Scottish archaeology could be accused of being theoretically conservative, or at least dependent on ideas and models developed elsewhere. A case-study looking at Neolithic studies will be used to illustrate that despite some recent critical historiographies of the study of the period in Scotland, archaeologists in Scotland and those working with Scottish material have been theoretically innovative and in step with wider paradigm changes. The study of the Neolithic in Scotland, it could be argued, has been shaped by theory more than the study of any other period; we are not isolated, but rather part of wider networks of discourse.

THE URBAN MIGRANT FUTURE DESIRE: A STUDY OF REVERSE MIGRATION IN MALAYSIA

2017 ◽  
Vol 3 (2) ◽  
pp. 177
Author(s):  
Nur Huzeima Mohd Hussain ◽  
Hugh Byrd ◽  
Nur Azfahani Ahmad
Keyword(s):  
Oil And Gas ◽  
Industrial Society ◽  
Peak Oil ◽  
Population Mobility ◽  
Reverse Migration ◽  
The Past ◽  
Urban Migrants ◽  
Urban Migrant ◽  
Oil Crisis

Globalisation combined with resources of oil and gas has led to an industrial society in Malaysia.  For the past 30 years, rapid urban growth has shifted from 73% rural to 73% urban population. However, the peak oil crisis and economic issues are threatening the growth of urbanisation and influencing the trends of population mobility. This paper documents the beginnings of a reverse migration (urban-to-rural) in Malaysia.  The method adopted case study that involves questionnaires with the urban migrants to establish the desires, definite intentions and reasons for future migration. Based on this data, it predicts a trend and rate of reverse migration in Malaysia. 

Conservation and Preservation of Nature Reserves, Monuments andSpecial Architectural or Historic Interest in Nigeria: Towards Promotion of Sustainable Cultural Tourism

2015 ◽  
Vol 3 (2) ◽  
pp. 201-218
Author(s):  
Francis Chuma Osefoh
Keyword(s):  
Cultural Tourism ◽  
Nature Reserves ◽  
Communication Link ◽  
Built Environments ◽  
Tourist Attraction ◽  
The Past ◽  
Personal Experiences ◽  
Historical Heritage ◽  
Developed Nations

Some of the renowned world tourism countries have special peculiarities in character in terms of their nature reserves and built environments; that made them stand out for their attractions and visits. These qualities range from conservation and preservation of nature reserves, built environments- epoch architectural supports over the years; historical heritage; political; religious; socio-economic; cultural; and  high technology that enhance culture. The virtues of multi- ethnic groups and multi- cultural nature gave Nigeria a rich cultural heritage, and she is blessed with natural wonders, unique wildlife, and a very favorable climate. More often than not less attention and importance are placed over the nature reserves and built environments to the detriment of tourism in lieu of other sectors. Summarily the country lacks the culture of conservation and preservation of her abundant resources to promote cultural tourism. Case study strategy was applied in the research tours with reports of personal experiences, documentaries and analyses of sites visited in Europe and Nigeria were highlighted with references to their attributes in terms of structures and features that made up the sites as relate to culture and attraction.The task in keeping rural, city landscapes and nature reserves alive stands out as the secret of communication link from the past to present and the future; which tourism developed nations reap as benefits for tourist attraction.

The Local Government of Kulon Progo Regency Innovation in Subduing Capitalism through Community Empowerment

2020 ◽  
Vol 4 (2) ◽  
pp. 229
Author(s):  
Muhammad Eko Atmojo ◽  
Helen Dian Fridayani
Keyword(s):  
Qualitative Method ◽  
Positive Impact ◽  
Community Empowerment ◽  
Case Study Approach ◽  
Study Approach ◽  
The Past ◽  
The People ◽  
District Government ◽  
The Government

Kulon Progo Regency is one of the districts that has many innovations, one of which is community empowerment in collaboration with a modern shop abbreviated as the shop name owned by the people (tomira). This research was motivated by the achievements of the Kulon Progo district government in carrying out development and innovation in the development of the Kulon Progo region by fully involving the Kulon Progo district community through community empowerment. This initiative was taken by the government of Kulon Progo Regency to improve community empowerment and protect the people of Kulon Progo Regency from various economic threats. Considering that in the past few years many modern shops have mushroomed in each district/city, so this is what makes Kulon Progo Regency move quickly to empower the community by collaborating between MSMEs or cooperative with modern shops. This study uses a qualitative method which case study approach. With the empowerment that has been done, the original products of Kulon Progo Regency or local products can be traded in modern stores so that local products in Kulon Progo Regency can compete with national products in these modern stores. The existence of such cooperation will indirectly improve the image of Kulon Progo Regency and lift the original products of Kulon Progo Regency. The lifting of the original products of Kulon Progo Regency will have a positive impact on the community, where indirectly the economy of the community will increase so that there will be prosperity for the community. Kabupaten Kulon Progo adalah salah satu kabupaten yang memiliki banyak inovasi, salah satunya adalah pemberdayaan masyarakat bekerja sama dengan toko modern disingkat nama toko yang dimiliki oleh masyarakat (tomira). Penelitian ini dilatarbelakangi oleh pencapaian pemerintah kabupaten Kulon Progo dalam melakukan pengembangan dan inovasi dalam pengembangan wilayah Kulon Progo dengan melibatkan sepenuhnya masyarakat kabupaten Kulon Progo melalui pemberdayaan masyarakat. Inisiatif ini diambil oleh pemerintah Kabupaten Kulon Progo untuk meningkatkan pemberdayaan masyarakat dan melindungi masyarakat Kabupaten Kulon Progo dari berbagai ancaman ekonomi. Menimbang bahwa dalam beberapa tahun terakhir banyak toko-toko modern telah menjamur di setiap kabupaten/kota, jadi inilah yang membuat Kabupaten Kulon Progo bergerak cepat untuk memberdayakan masyarakat dengan berkolaborasi antara UMKM atau bekerjasama dengan toko-toko modern. Penelitian ini menggunakan metode penelitian kualitatif dengan pendekatan studi kasus, dengan metode yang digunakan adalah dokumentasi. Dengan pemberdayaan yang telah dilakukan, produk asli Kabupaten Kulon Progo atau produk lokal dapat diperdagangkan di toko modern sehingga produk lokal di Kabupaten Kulon Progo dapat bersaing dengan produk nasional di toko modern ini. Adanya kerjasama tersebut secara tidak langsung akan meningkatkan citra Kabupaten Kulon Progo dan mengangkat produk asli Kabupaten Kulon Progo. Pencabutan produk asli Kabupaten Kulon Progo akan berdampak positif bagi masyarakat, di mana secara tidak langsung perekonomian masyarakat akan meningkat sehingga akan ada kesejahteraan bagi masyarakat.

A LOOK INTO THE EARTH: EVALUATING THE USE OF MAGNETIC SURVEY IN AFRICAN ARCHAEOLOGY

2004 ◽  
Vol 2 (1) ◽  
pp. 49-63 ◽  
Author(s):  
Carlos Magnavita ◽  
Norbert Schleifer
Keyword(s):  
Geophysical Methods ◽  
Field Research ◽  
Archaeological Sites ◽  
Magnetic Survey ◽  
The Past ◽  
Common Technique ◽  
Sub Saharan ◽  
Prehistoric Settlements ◽  
Present Case Study

In the last decades, geophysical methods such as magnetic survey have become a common technique for prospecting archaeological sites. At sub-Saharan archaeological sites, however, magnetic survey and correlated techniques never came into broad use and there are no signs for an immediate change of this situation. This paper examines the magnetic survey undertaken on the Nigerian site of Zilum, a settlement of the Gajiganna Culture (ca 1800-400 BC) located in the Chad Basin and dated to ca 600-400 BC. By means of the present case study, we demonstrate the significance of this particular type of investigation in yielding complementary data for understanding the character of prehistoric settlements. In conclusion, we point out that geophysical methods should play a more important role in modern archaeological field research, as they furnish a class of documentation not achievable by traditional survey and excavation methods, thus creating new perspectives for interpreting the past of African societies.

Disability and Work During the Industrial Revolution in Britain

2018 ◽  
Author(s):  
Daniel Blackie
Keyword(s):  
Disability Studies ◽  
Industrial Development ◽  
Industrial Revolution ◽  
Coal Industry ◽  
Historical Research ◽  
Disabled People ◽  
Industrial Sites ◽  
The Past ◽  
Paid Employment

A common claim in disability studies is that industrialization has marginalized disabled people by limiting their access to paid employment. This claim is empirically weak and rests on simplified accounts of industrialization. Use of the British coal industry during the period 1780–1880 as a case study shows that reassessment of the effect of the Industrial Revolution is in order. The Industrial Revolution was not as detrimental to the lives of disabled people as has often been assumed. While utopian workplaces for disabled people hardly existed, industrial sites of work did accommodate quite a large number of workers with impairments. More attention therefore needs to be paid to neglected or marginalized features of industrial development in the theorization of disability. Drawing on historical research on disability in the industrial workplace will help scholars better understand the significance of industrialization to the lives of disabled people, both in the past and the present.

Prohibition, Legalization, and Political Consumerism

2018 ◽  
pp. 740-769 ◽  
Author(s):  
Elizabeth A. Bennett
Keyword(s):  
Social Movements ◽  
Legal Status ◽  
Ethical Issues ◽  
Drug Control ◽  
Psychoactive Substance ◽  
Political Consumerism ◽  
Control Laws ◽  
The Past ◽  
The Us

Cannabis (marijuana) is the most commonly consumed, universally produced, and frequently trafficked psychoactive substance prohibited under international drug control laws. Yet, several countries have recently moved toward legalization. In these places, the legal status of cannabis is complex, especially because illegal markets persist. This chapter explores the ways in which a sector’s legal status interacts with political consumerism. The analysis draws on a case study of political consumerism in the US and Canadian cannabis markets over the past two decades as both countries moved toward legalization. It finds that the goals, tactics, and leadership of political consumerism activities changed as the sector’s legal status shifted. Thus prohibition, semilegalization, and new legality may present special challenges to political consumerism, such as silencing producers, confusing consumers, deterring social movements, and discouraging discourse about ethical issues. The chapter concludes that political consumerism and legal status may have deep import for one another.

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