1,721,399 research outputs found
Optimizing electronic cooling: Harnessing potentials of impinging jet flows with metal foam heat sinks for superior thermal management
No full textEffective heat dissipation is essential for cooling power-intensive chips and densely packed electronics with significant heat output such as those used in data centers. This study explores the hybrid thermal management strategies that combine the use of impinging jet flow (IJF) and high-porosity metal foam (MF) heat sinks to enhance convective heat transfer. Unlike conventional jet cooling systems, the integration of metal foam introduces a highly conductive, porous medium that amplifies surface area, promotes flow mixing, and accelerates thermal diffusion — resulting in 1 - 2 times higher heat transfer compared to clear cases (CC). A 2D axisymmetric numerical model is developed in ANSYS Fluent using the Reynolds-Averaged Navier–Stokes (RANS) equations with the standard k-ε turbulence model. The setup features a single circular nozzle, aluminum target plate, aluminum metal foams with air as a cooling fluid. Key parameters including nozzle-to-plate spacing (IH = 2.8 – 8.5), Peclet number (Pe = 2200 – 17,000), and foam porosity (ε = 0.90 – 0.95) — are systematically varied. The findings indicate that minimizing porosity and internal heating (IH) substantially enhances heat transfer performance. A novel correlation for average Nusselt number (Nu ̅) has been developed, accompanied by an enhancement factor that quantifies the thermal improvement across the analyzed configurations. This work provides a robust framework for optimizing hybrid cooling systems and can be extended to explore alternative working fluids, foam geometries, and transient thermal loads in future studies
Porous pathways to chill: Unravelling the influence of metal foam characteristics on heat transfer dynamics through experimental investigation
No full textDo Energy Transition and International Tourism Mitigate Environmental Emissions? The Case of SCO Economies: Muhammad Sajid Ameen, Feroze Ali, and Muhammad Atiq-ur-Rehman
Full text linkThis study examines the role of energy transition and international tourism in alleviating environmental emissions in the case of selected Shanghai Cooperation Organization (SCO) countries for 1992–2022. Ecological footprint has been taken as a proxy for environmental emissions. Along with energy transition and international tourism, GDP per capita is also incorporated as an independent variable to check the validity of the Environmental Kuznets Curve (EKC) hypothesis. To find the cross-sectional dependency among selected economies, the cross-sectional dependence (CD) test was used. Due to geographical reasons, cross-country spillover special effects are possible among the eight SCO economies. After testing the unitroots of the variables, two empirical approaches have been used for the empirical findings: fixed effect regression with Driscoll-Kraay (DK) standard errors and the method of moment’s quintile regression (MMQR). The empirical results indicate that the EKC hypothesis is not valid in the case of the eight selected SCO countries. Though energy transition has reduced environmental emissions in the economies under consideration, the impact of international tourism on the population is statistically insignificant. We can conclude and propose for countries in this region to focus on renewable energy source
Revival of Legacy of Tooke and Gibson: Further Evidence and Implications for Monetary Policy
No full textAbstractTraditional economics assumes that interest rate effects inflation by changing the aggregate demand (Barth and Ramay, 2002). On the other hand, many economists in recent years have explored the cost side effects of monetary transmission and found very strong evidences in favour of cost channel. One of such studies is that by Rehman (2015) which explores the relationship between interest rate and inflation for a large data set comprising various measures of interest rate and inflation from countries around the globe. Rehman (2015) computes the correlation between two variables and he finds that the correlation between two variables is either positive or insignificant. Rehman argues that the finding is quite robust and does not change with a change in measure of interest rate and/or inflation. If the correlation between interest rate and inflation is positive then using interest rate to control inflation would be counterproductive. Thus it will endorse the warning of Wright Patman, a US congressman and Chairman of Joint Economic Committee who argues that “senseless of trying to fight inflation by raising interest rate, throwing the gasoline on fire to put out the flames would be as logical”. Findings of Rehman (2015) are based on correlation coefficients. The correlation without having control variables could only provide a clue and could be subject to serious missing variable bias. However, Rehman (2015) argues that thousands of similar clues from the entire globe collectively become very strong evidence. However, given the importance of the topic, it is necessary to do a more careful analysis and summarize the relationship between two variables which is not subject to missing variable bias. Therefore, this paper applies more sophisticated econometric techniques including Granger Causality and Static Long Run Solution to find the impact of interest rate and inflation.</jats:p
Revival of Legacy of Tooke and Gibson: Implications for Monetary Policy
No full textAbstract
The monetary policy rules used by central banks these days are based on the assumption that inflation could be reduced by increasing interest rate. On contrary, Tooke (1774-1858), the forefather of monetary economics, was of the view that the relationship between interest rate and inflation should be positive. His view was based on simple logic, ‘interest is a part of cost, and therefore, the increase in interest rate should increase inflation by increasing cost of production (Tooke, 1838)’. Tooke’s view has got support from a number of empirical evidence including Gibson (1923) who found positive correlation between two variables for UK data over a period of 200 years. On the other hand, mainstream economic thinking on which the actual monetary practices are based ignored any possibility of positive relationship between interest rate and inflation throughout the history. The existence of Tooke’s cost side effects of monetary policy is a serious concern because if these effects exist than the use of monetary policy would be counterproductive. Using the data from entire globe, I attempt to explore the nature of relationship between the interest rate and inflation. I found that the data supports the perception of Tooke and Gibson and denies that the effectiveness of monetary policy currently adapted by the correlation between interest rate and inflation is positive. The results are robust to sample size, sample period, and various definitions of interest rate and inflation.</jats:p
Impact of Model Specification Decisions on Unit Root Tests
Full text linkPerformance of unit tests depends on several specification decisions prior to their application e.g., whether or not to include a deterministic trend. Since there is no standard procedure for making such decisions, therefore the practitioners routinely make several arbitrary specification decisions. In Monte Carlo studies, the design of DGP supports these decisions, but for real data, such specification decisions are often unjustifiable and sometimes incompatible with data. We argue that the problems posed by choice of initial specification are quite complex and the existing voluminous literature on this issue treats only certain superficial aspects of this choice. We also show how these initial specifications affect the performance of unit root tests and argue that Monte Carlo studies should include these preliminary decisions to arrive at a better yardstick for evaluating such tests.model specification, trend stationary, difference stationary
Impact of Hydropower Projects on Economic Growth of AJK.
Full text linkAccording to official estimates, territory of Azad Jammu & Kashmir has a potential to generate about 4600 MW of hydroelectricity, the cheapest source of energy. Total deficit in energy Pakistan is facing these days is about 5000 MW. So, only AJK can fulfill more than 90% of deficit of now demanded energy for entire country. Beside this direct and explicit advantage of hydropower projects to power sector, these projects may be extremely useful in improving many economic and social indicators at local and national level. Many socioeconomic indicators reveal that Azad Kashmir is there is huge gap in development level of AJK and National level. Development of power sector is extremely important to fill this gap. In this paper, we analyze effect of possible implementation of these projects on various economic and social sectors at local and national level. We discuss the obstacles in implementation of projects and recommendations are given at the end
Model specification, observational equivalence and performance of unit root tests
Full text linkIn this paper we highlight the necessity of new criteria for evaluation of performance of unit root tests. We suggest focusing directly on the reasons that create ambiguity in unit root test’s results. Two reasons for unsatisfactory properties of unit root tests can be found in the literature (i) the model misspecification and (ii) observational equivalence. Regarding first reason, there is immense literature on several components of model specification covering specification techniques, consequence of misspecification and robust methods. However complete model specification involves multiple decisions and most of studies on performance of unit root tests do not address issue of multiple specification decisions simultaneously. The Monte Carlo studies are conditional on some of implicit specification and for Monte Carlo; these specifications are by construction valid. But for real data, the implicit decisions are often not true and specification decisions need to be endogenized. A closer match with real case is possible if multiple specification decisions are endogenized, thus providing more reliable measure of performance of unit root tests. Second problem in differentiating trend and difference stationary process is the observational equivalence between two processes. We suggest exploring data generating processes with different long run dynamics and small sample equivalence so that a researcher should have an idea about other plausible models for a data set for which he has estimated some model
Most Stringent Test for Location Parameter of a Random Number from Cauchy Density
Full text linkWe study the test for location parameter of a random number from Cauchy density, focusing on point optimal tests. We develop analytical technique to compute critical values and power curve of a point optimal test. We study the power properties of various point optimal tests. The problem turned out to be different in its nature, in that, the critical value of a test determines the power properties of test. We found that if for given size and any point m in alternative space, if the critical value of a point optimal test is 1, the test optimal for that point is the most stringent test.Cauchy density, Power Envelop, Location Parameter, Stringent Test
Most Stringent Test for Location Parameter of a Random Number from Cauchy Density
Full text linkWe study the test for location parameter of a random number from Cauchy density, focusing on point optimal tests. We develop analytical technique to compute critical values and power curve of a point optimal test. We study the power properties of various point optimal tests. The problem turned out to be different in its nature, in that, the critical value of a test determines the power properties of test. We found that if for given size α and any point θm in alternative space, if the critical value of a point optimal test is 1, the test optimal for that point is the most stringent test
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