Interaction of Shear and Bending on Light Gage Steel Diaphragms

In the modern practice of design of structures a variety of problems confront the structural engineer. Whether he is involved in the area of aircraft structures (i.e. stressed skin structures) or complex immovable structures, the problems are seldom simple. In the design of stressed skin structures the complexity and the refinements of analysis methods, combined with the economics of weight saving, do create many problems to be solved. Interaction of multiple force systems are among the problems of the engineer. Many types of interaction occur in practical structures. Some interaction behavior is predictable though routine stress analysis such as the computation of maximum stresses in a short block subjected to bending and axial force. Other interaction has been expressed through a combination of theory and substantial testing such as the column design formulas found in many standard specifications. Some cases of combined loading involve such complex structural behavior that an exact analytical approach even if available would be of doubtful value. Theoretical approaches must of necessity contain many fundamental assumptions which are difficult to either justify or verify because of the problem complexity. It is also noted that, in recent years, the use of light gage steel has been increasing in construction. Civil engineers are beginning to recognize that many portions of a structural framework can participate as a unit in resisting all of the forces as well as local forces applied to single members. The complexity of loading problems and lack of enough test-proved literature, prevent the designers from using many elements under combined load applications. There is a need for research in many areas of combined loading. Theoretical or empirical formulae should be available to the design engineer for use without requiring highly complex theoretical calculations. This thesis concerns the investigation and testing of a series of panel specimens for the condition of combined shear and bending loads. These panels represent small scale versions of panels used as either the web of a beam or the roof of the building. As a web in a beam, these panels must carry in-plane shearing forces much like the web of a plate grinder. Roof loads provide transverse forces which require the panel to carry as a beam the bending type loads between the edge members. Using the results of the test data, it has been possible to verify that the interaction formula applicable to this type of structure is a circular one

HT-FED2004-56528 DEVELOPMENT AND EXPERIMENTAL VALIDATION OF AN EXERGY-BASED COMPUTATIONAL TOOL FOR DATA CENTER THERMAL MANAGEMENT

ABSTRACT The recent miniaturization of electronic devices and compaction of computer systems will soon lead to data centers with power densities of the order of 300 W/ft 2 . At these levels, traditional thermal management techniques are unlikely to suffice. To enable the dynamic smart cooling systems necessary for future data centers, an exergetic approach based on the second law of thermodynamics has recently been proposed. However, no experimental data related to this concept is currently available. This paper discusses the development and subsequent validation of an exergy-based computer model at an instrumented data center in Palo Alto, California. The study finds that when appropriately calibrated, such a computational tool can successfully predict information about local and global thermal performance that cannot be perceived intuitively from traditional design methods. Further development of the concept has promising potential for efficient data center thermal management

Global, regional, and national burden of disorders affecting the nervous system, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BackgroundDisorders affecting the nervous system are diverse and include neurodevelopmental disorders, late-life neurodegeneration, and newly emergent conditions, such as cognitive impairment following COVID-19. Previous publications from the Global Burden of Disease, Injuries, and Risk Factor Study estimated the burden of 15 neurological conditions in 2015 and 2016, but these analyses did not include neurodevelopmental disorders, as defined by the International Classification of Diseases (ICD)-11, or a subset of cases of congenital, neonatal, and infectious conditions that cause neurological damage. Here, we estimate nervous system health loss caused by 37 unique conditions and their associated risk factors globally, regionally, and nationally from 1990 to 2021.MethodsWe estimated mortality, prevalence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs), with corresponding 95% uncertainty intervals (UIs), by age and sex in 204 countries and territories, from 1990 to 2021. We included morbidity and deaths due to neurological conditions, for which health loss is directly due to damage to the CNS or peripheral nervous system. We also isolated neurological health loss from conditions for which nervous system morbidity is a consequence, but not the primary feature, including a subset of congenital conditions (ie, chromosomal anomalies and congenital birth defects), neonatal conditions (ie, jaundice, preterm birth, and sepsis), infectious diseases (ie, COVID-19, cystic echinococcosis, malaria, syphilis, and Zika virus disease), and diabetic neuropathy. By conducting a sequela-level analysis of the health outcomes for these conditions, only cases where nervous system damage occurred were included, and YLDs were recalculated to isolate the non-fatal burden directly attributable to nervous system health loss. A comorbidity correction was used to calculate total prevalence of all conditions that affect the nervous system combined.FindingsGlobally, the 37 conditions affecting the nervous system were collectively ranked as the leading group cause of DALYs in 2021 (443 million, 95% UI 378–521), affecting 3·40 billion (3·20–3·62) individuals (43·1%, 40·5–45·9 of the global population); global DALY counts attributed to these conditions increased by 18·2% (8·7–26·7) between 1990 and 2021. Age-standardised rates of deaths per 100 000 people attributed to these conditions decreased from 1990 to 2021 by 33·6% (27·6–38·8), and age-standardised rates of DALYs attributed to these conditions decreased by 27·0% (21·5–32·4). Age-standardised prevalence was almost stable, with a change of 1·5% (0·7–2·4). The ten conditions with the highest age-standardised DALYs in 2021 were stroke, neonatal encephalopathy, migraine, Alzheimer's disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications due to preterm birth, autism spectrum disorder, and nervous system cancer.InterpretationAs the leading cause of overall disease burden in the world, with increasing global DALY counts, effective prevention, treatment, and rehabilitation strategies for disorders affecting the nervous system are needed

Two-Phase Loop: Compact Thermosyphon

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Thermal Considerations in Cooling Large Scale High Compute Density Data Centers

A high compute density data center of today is characterized as one consisting of thousands of racks each with multiple computing units. The computing units include multiple microprocessors, each dissipating approximately 250 W of power. The heat dissipation from a rack containing such computing units exceeds 10 KW. Today's data center, with 1000 racks, over 30,000 square feet, requires 10 MW of power for the computing infrastructure. A 100,000 square foot data center of tomorrow will require 50 MW of power for the computing infrastructure. Energy required to dissipate this heat will be an additional 20 MW. A hundred thousand square foot planetary scale data center, with five thousand 10 KW racks, would cost ~$44 million per year (@$100/MWh) just to power the servers & $18 million per year to power the cooling infrastructure for the data center