886 research outputs found
Cyclic performance and strengthening of built-up battened columns
Built-up battened columns have been widely used in steel structures mainly because of providing a higher moment of inertia than solid sections with a similar weight. Despite wide application in steel constructions, the seismic design of these columns has not been well addressed in the literature, and seismic design codes do not provide a specific seismic design guideline for them. On the other hand, past earthquakes have shown that built-up battened columns have been vulnerable against seismic actions mainly because of the plastic deformation in battens, fracture of battens, global buckling of columns, local buckling of web and flanges, and formation of plastic hinges at their bottom panel. Therefore, their seismic behaviour should be investigated, and an efficient strengthening method should be proposed. In this study, experimental works and numerical simulations were conducted to investigate the governing failure modes of built-up batten columns. Besides, the effect of batten's thickness, battens spacing, chord distance and axial load on the ultimate load, ductility ratio, stiffness degradation rate and energy dissipation capacity of built-up battened columns were investigated through quasi-static cyclic loading. This study also proposed a strengthening method through the filling of chords with grout and wrapping it with carbon fibre reinforced polymer (CFRP). Experimental works included four unstrengthen and four strengthened columns with different battens spacing and chord distances. Besides, 210 built-up battened columns with different batten thicknesses, battens spacing, chord distances, axial forces, number of CFRPs layers and number of strengthened panels were simulated in ABAQUS software and subjected to cyclic loading. The obtained results indicated that the bulging of chord webs together with the local buckling of chord flanges were the main reason for the failure of columns. Moreover, built-up columns did not reach their plastic moment capacity because of local buckling in flanges. Furthermore, the columns with 62 mm batten spacing showed a 30% larger ultimate load than that of the column with 550 mm batten spacing. The results also indicated that the columns with 62 mm batten spacing reached 95.91% of their theoretical bending capacity. It was shown that design codes" requirements for batten spacing was not conservative and did not result in an identical safety margin for the bending moment capacity of built-up columns. An increase in the chord distance from 50 mm to 150 mm enhanced the lateral strength of the column by 35%. On the other hand, an increase in the axial force from 0.1Fy to 0.4Fy decreased the lateral strength and ultimate displacement by 24% and 36%, respectively. The displacement ductility ratios of the unstrengthen built-up battened columns were less than two even when subjected to an axial compression ratio smaller than 0.2. The results indicated that CFRP application delays/shifts the local buckling of flanges and bulging of the web to the upper un-retrofitted panels; however, an increase in the number of CFRPs layers did not show any pronounced effect. The retrofitting of columns resulted in a significant increase in the lateral strength and corresponding displacement by 32.15% and 39.34%, respectively, as compared to the un-retrofitted columns. The energy dissipation capacity of retrofitted columns was 66.39% higher than that of the un-retrofitted columns. The retrofitted columns lost 27%, while the un-retrofitted columns lost 52% of their initial lateral stiffness at a drift ratio of 5.0%. In addition, the retrofitted columns were also able to reach their plastic moment capacity and had a displacement ductility ratio larger than two. The outcome of this study helps practice engineers to understand the seismic behavior of built-up battened columns better and provides an efficient retrofitting method for these columns
The Employment Effect of Innovation: Evidence from Bangladesh and Pakistan
The analysis of the impact of innovation on employment growth
is an important topic for policy-makers. Unemployment is an important
social topic, and the effects of innovation on employment are often
poorly understood. Despite the significance of this relationship, very
few studies on this topic are yet available for developing countries
compared with the developed ones. This paper contributes to this scant
literature by investigating the employment effects of innovation for two
South Asian developing countries: Bangladesh and Pakistan. We further
analyse whether this relationship shows country-specific and
industry-specific differences. Our analysis shows that both product and
process innovation spur employment in this region as a whole, in both
low-tech and high-tech industries, even after controlling for a number
of firm-specific characteristics. Moreover, although both innovation
types also have significant, positive impacts on employment growth of
all Bangladeshi and of all Pakistani firms separately, they are
important factors for employment growth of only high-tech Bangladeshi
firms and of only low-tech Pakistani firms. Contrary to most previous
studies, we witness an insignificant effect of growth of labour cost on
employment growth, perhaps due to the availability of cheaper labour
force compared with the developed countries. We notice that some of the
innovation determinants exert different influences across industries and
across both countries. The same holds true for the determinants of
employment growth. JEL Classification: J23, O31, O33 Keywords:
Bangladesh, Employment Growth, Pakistan, Product Innovation, Process
Innovatio
Human Capital and Economic Growth: Time Series Evidence from Pakistan
Human capital is generally considered as a positive contributor in the economic growth. In this study, we estimate this relationship using time series data of Pakistan for the period 1978 to 2007. A health adjusted education indicator for human capital is used in the standard Cobb-Douglas production function confirms the long run positive relationship between human capital and the economic growth in Pakistan. A sensitivity analysis was also performed in order to check the robustness of the initial findings. The estimation results supported the findings of the previous studies that human capital is positively related to growth and also that the results are robust. The health adjusted education indicator was found to be a highly significant determinant of economic growth, which indicates that both the health and education sectors should be given special attention in order to ensure long run economic growth.Human Capital, Economic Growth, Education and Health
Failures of land tenancy in Pakistan
The Government of Sindh must urgently come up with measures to improve land tenancy to ensure the end of bonded labour. Drawing on fieldwork from the region, Abdul Waheed Jamali explores the plight of bonded labourers and the failures of the current Sindh Tenancy Act
Protecting small farmers in Pakistan in the wake of the new seed Act
As a result of the Seed (Amendment) Act, farmer friendly seed policies have been replaced by legislation which favours multinational corporations. Abdul Waheed Jamali discusses why this is a problem, and draws on Sindh as a case study to explore how state governments can support existing public bodies to support small farmers
Investigation of doping and photoexcitation in carbon nanotubes using Raman spectroscopy
La spectroscopie Raman est une technique de caractĂ©risation non destructive appropriĂ©e pour l'Ă©tude des nanotubes des carbone. Des diffĂ©rences dans le dĂ©calage spectral des bandes Raman D et G, correspondant aux effets anharmoniques, sont observĂ©es lors d'un chauffage des nanotubes de carbone par irradiation photonique intense ou en faisant varier la tempĂ©rature d'un thermostat. Les modifications spectrales du mode D sont attribuĂ©s Ă des modifications du processus de double rĂ©sonance Raman en raison de la variation de la structure de bande Ă©lectronique provoquĂ©e par la creation des excitons. L'enquĂȘte de l'influence du dopage et de photoexcitation sur la bande G et la D de nanotubes de carbone montrent que la spectroscopie Raman peut ĂȘtre utilisĂ© comme un outil de diagnostic. Les bandes spectrales Ă©largir et dĂ©cale vers le haut frĂ©quence pour l'azote dopĂ© nanotubes de carbone multi parois. Le dĂ©calage vers le haut frĂ©quence pour l'acide sulfurique dopĂ© double parois nanotubes de carbone est attribuĂ©e Ă transfert de charge et la dĂ©formation dans le rĂ©seau. Nous avons combinĂ© le dopage de l'acide sulfurique et haute pression spectroscopie Raman pour Ă©tudier les propriĂ©tĂ©s de DWCNT. Le DWCNT dopĂ© avec diffĂ©rentes concentrations d'acide sulfurique sous haute pression, suggĂšre un effet de l'ordre des molĂ©cules autour de nanotubes Ă concentrations d'acide supĂ©rieur. Spectres Raman de double parois nanotube de carbone individual sur la silice en Ă©vidence un Ă©clatement de la bande G grĂące aux contributions du tube interne et externe lorsque utilisez une Ă©nergie d'excitation en rĂ©sonance avec le tube mĂ©tallique interne et tube semionducteurs externe. Les largeurs des bandes sont comparables Ă ce qui a Ă©tĂ© observĂ© pour le nanotube de carbone monoparoi individul ou le graphĂšne. Augmentation de la puissance du laser dĂ©cale la bande G du tube extĂ©rieur vers les Ă©nergies plus Ă©levĂ©es et modifie sa forme en ligne.Raman spectroscopy is a non-invasive characterization technique suitable for the study of carbon nanotubes. Differences in the spectral shift of the Raman D and G bands are observed when heating carbon nanotubes through intense photon irradiation and by varying the temperature in a thermostat. These spectral changes in D mode are attributed to the variation of the electronic band structure by excitons creation. The investigation of the influence of doping and photoexcitation on the Raman G and D band of carbon nanotubes show that Raman spectroscopy can be used as a diagnostic tool. The spectral bands broaden and up shifts for nitrogen doped multi walled carbon nanotubes (MWCNT). The up shift for sulphuric acid doped double wall carbon nanotubes (DWCNT) synthesized from catalytic chemical vapor deposition method (CCVD) is attributed to charge transfer and strain in the lattice. We have combined sulphuric acid doping and high pressure Raman spectroscopy to investigate the properties of DWCNT. The DWCNT doped with different concentrations of sulphuric acid are explored under high pressure suggesting an effect of the molecular ordering around carbon nanotubes at higher acid concentrations. Raman spectra of individual double wall carbon nanotubes on silica show a splitting of the G band due to contributions of the inner and outer tube when using a excitation energy in resonance with the inner metallic tube and outer semiconducting tube. The spectral line widths are comparable to what has been observed for individual single wall carbon nanotubes (SWCNT) or graphene. Increased laser power shifts the G band of the outer tube to higher energies and modifies its line shape
The Challenges of Distance Education
Education is of extreme importance as it is key to equipping the workforce with the skills needed to develop national economies. The importance is exemplified by the Education for All movement, a global commitment to provide quality basic education for all children, youth and adults, which links directly to the UN Millennium Development Goals (MDGs). Sustainable development of quality primary education is dependent on complementary development in the secondary and tertiary education sectors. With economies relying more and more on the generation and application of knowledge, productivity is increasingly dependent on the development and spread of technological innovation. Higher education and life-long learning are today more important to development than ever before, due to the role knowledge plays in development - knowledge is power
Effects of Terms of Trade and its Volatility on Economic Growth: A Cross Country Empirical Investigation
This study examines the effects of terms of trade and its volatility on economic growth for a sample of 94 developed and developing countries, using five year average annual data from 2004 to 2008. The cross country ordinary least square estimation results indicate significant positive effect of terms of trade on economic growth. Furthermore, volatility of terms of trade has significant positive effect on economic growth. To test the robustness of initial results, sensitivity analysis has been performed using different additional variables, sample size and various proxies of volatility variable. The initial results were found robust despite the inclusion of various variables in the basic model and use of various proxies for volatility of terms of trade.Terms of trade, Volatility, Economic Growth
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