Narrow Results

Recent trends in processor power for the next generation devices point clearly to significant increase in processor heat dissipation over the coming years. In the desktop system design space, the tendency has been to minimize system enclosure size while maximizing performance, which in turn leads to high power densities in future generation systems. The current thermal solutions used today consist of advanced heat sink designs and heat pipe designs with forced air cooling to cool high power processors. However, these techniques are already reaching their limits to handle high heat flux, and there is a strong need for development of more efficient cooling systems which are scalable to handle the high heat flux generated by the future products.

To meet this challenge, there has been research in academia and in industry to explore alternative methods for extracting heat from high-density power sources in electronic systems. This talk will discuss the issues surrounding device cooling, from the transistor level to the system level, and describe system-level solutions being developed for desktop computer applications developed in our group at Stanford University.

The continuing LH2 R & D by the MuCool group, conducted by Illinois Consortium for Accelerator Research (ICAR) institutions (NIU, IIT and UIUC), the University of Mississippi, Oxford University and Fermilab, are summarized here, including results for the first hydrogen tests of an absorber prototype from Osaka University and KEK cooled by internal convection at the newly constructed FNAL MuCool Test Area (MTA). The program includes designs for the high-powered test of an absorber prototype (external heat exchange) at the MTA which are nearing completion to be installed by fall 2005, an alternative absorber design (internal heat exchange) being finalized for the approved cooling experiment (MICE) at Rutherford-Appleton Laboratory, and a novel idea for gaseous hydrogen absorbers being developed at Fermilab for a high powered test at the MTA in 2006.

Welding, despite being the most efficient joining process, has significant negative impact on the environment and worker health. This paper presents the environmental impact of various conventional welding processes and sustainability of Friction Stir Welding–a Green technology which requires no filler material, no shielding gas, no flux and involves no gas emissions. It is an energy-efficient process that saves significant amount of power and energy when compared to conventional welding processes. The defect-free welds produced have better mechanical and metallurgical properties than other processes. The higher temperature distributed due to the friction heat is established as the source of weld failure. Cooling the weld joint controls the heat conduction thus further enhancing the weld properties. This review paper explores the different cooling techniques employed for cooling the joint during Friction Stir Welding process. The changes in temperature distribution and microstructure caused by the cooling applied and the consequential transformation in material flow, tensile strength, hardness, corrosion, wear, residual stress are discussed. The changes in weld properties obtained by using different cooling media on different materials are reviewed.

The dynamics of dispersive optical solitons, modeled by Schrödinger–Hirota equation, are studied in this paper. Bright, dark and singular optical soliton solutions to this model are obtained in presence of perturbation terms that are considered with full nonlinearity. Soliton perturbation theory is also applied to retrieve adiabatic parameter dynamics of bright solitons. Optical soliton cooling is also studied. Finally, exact bright, dark and singular solitons are addressed for birefringent fibers with perturbation terms included.

The Potential of Saving Human Lives with Hibernation.

Classical ways of cooling require some of these elements: phase transition, compressor, nonlinearity, valve and/or switch. A recent example is the 2018 patent of Linear Technology Corporation; they utilize the shot noise of a diode to produce a standalone nonlinear resistor that has $T$/2 noise temperature (about 150K). While such “resistor” can cool its environment when it is AC coupled to a resistor, the thermal cooling effect is only academically interesting. The importance of the invention is of another nature: In low-noise electronics, it is essential to have resistors with low-noise temperature to improve the signal-to-noise ratio. A natural question is raised: can we use a linear system with feedback to cool and, most importantly, to show reduced noise temperature? Exploring this problem, we were able to produce standalone linear resistors showing strongly reduced thermal noise. Our must successful test shows $T$/100 (about 3K) noise temperature, as if the resistor would have been immersed in liquid helium. We also found that there is an old solution offering similar results utilizing the virtual ground of an inverting amplifier at negative feedback. There, the “cold” resistor is generated at the input of an amplifier. On the other hand, our system generates the “cold” resistance at the output, which can have practical advantages.

Superconducting devices such as magnets and cavities are key components in the accelerator field for increasing the beam energy and intensity, and at the same time making the system compact and saving on power consumption in operation. An effective cryogenic system is required to cool and keep the superconducting devices in the superconducting state stably and economically. The helium refrigeration system for application to accelerators will be discussed in this review article. The concept of two cooling modes — the liquefier and refrigerator modes — will be discussed in detail because of its importance for realizing efficient cooling and stable operation of the system. As an example of the practical cryogenic system, the TRISTAN cryogenic system of KEK Laboratory will be treated in detail and the main components of the cryogenic system, including the high-performance multichannel transfer line and liquid nitrogen circulation system at 80 K, will also be discussed. In addition, we will discuss the operation of the cryogenic system, including the quench control and safety of the system. The satellite refrigeration system will be discussed because of its potential for wide application in medium-size accelerators and in industry.

High energy ion colliders are large research tools in nuclear physics for studying the quark–gluon–plasma (QGP). The collision energy and high luminosity are important design and operational considerations. The experiments also expect flexibility with frequent changes in the collision energy, detector fields, and ion species. Ion species range from protons, including polarized protons in RHIC, to heavy nuclei like gold, lead, and uranium. Asymmetric collision combinations (such as protons against heavy ions) are also essential. For the creation, acceleration, and storage of bright intense ion beams, limits are set by space charge, charge change, and intrabeam scattering effects, as well as beam losses due to a variety of other phenomena. Currently, there are two operating ion colliders: the Relativistic Heavy Ion Collider (RHIC) at BNL and the Large Hadron Collider (LHC) at CERN.

I review some accelerator physics topics for circular as well as linear colliders, considering both lepton and hadron beams.

In the present paper, the effect of desorption temperature on the performance of adsorption cooling systems driven by waste heat from fuel cells was analyzed. The studied adsorption cooling systems employ activated carbon fiber (ACF) of type A-20–ethanol and RD type silica gel–water as adsorbent–refrigerant pairs. Two different temperature levels of waste heat from polymer electrolyte fuel cell (PEFC) and solid oxide fuel cell (SOFC) are used as the heat source of the adsorption cooling systems. The adsorption cycles consist of one pair of adsorption–desorption heat exchanger, a condenser and an evaporator. System performance in terms of specific cooling capacity (SCC) and coefficient of performance (COP) are determined and compared between the studied two systems. Results show that silica gel–water based adsorption cooling system is preferable for effective utilization of relatively lower temperature heat source. At relatively high temperature heat source, COP of ACF–ethanol based adsorption system shows better performance than that of silica gel–water based adsorption system.

The human thermal comfort and the indoor healthy air quality in the houses and the offices have become a vital necessity, especially in the state of the development of the contagious virus as the COVID-19. In this study, the evaluation of the air distribution was investigated using a DHTT sensor connected to an ARDUINO card to benefit their simple use and their reasonable price comparing to other tools such as the infrared camera. The measurement of the temperature is made in 14 points divided on two directions: one near the sitting manikin and another in front with the cooling system. The impact of the heat sources was tested. In these conditions, the indoor temperature was examined for an empty room, a room occupied by one person and one computer, a room occupied by two persons and two computers and a lighted room. The experimental results prove that the indoor temperature increases with the multiplication of the heat sources. From a temperature equal to $T=32^{\circ }$C, the PMV curves move away from the comfort zone and the indoor climate becomes hot.

Metalworking fluids (MWFs) play a crucial role in machining processes by lubricating and cooling cutting tools, reducing friction, and improving overall machining efficiency. These fluids can be classified into various types, including cutting oils, water-based fluids, and semi-synthetic or synthetic fluids. Cutting oils are often mineral-based, providing excellent lubrication in heavy-duty applications. Water-based fluids, on the other hand, are more environmentally friendly and commonly used in light to moderate machining operations. Semi-synthetic and synthetic fluids offer a balance between performance and eco-friendliness, incorporating additives to enhance their properties. Proper selection and management of MWFs are essential for optimizing tool life, surface finish, and overall productivity in metal machining applications. Research has shown that the cost of cutting fluid in machining constitutes 17% of the total production cost. In the same research, it was stated that the cutting tool cost was around 4%. This review provides an overview of the current advancements in sustainable MWFs within machining applications. It explores state-of-the-art technologies, formulations, and practices aimed at minimizing environmental impact while maintaining optimal performance in metalworking processes. The review encompasses eco-friendly additives, recycling methods, and emerging trends in the development of MWFs, emphasizing the importance of sustainable practices in the manufacturing industry.

We present two recent parametrizations of the equation of state (FSU2R and FSU2H models) that reproduce the properties of nuclear matter and finite nuclei, fulfill constraints on high-density matter stemming from heavy-ion collisions, produce 2M_⊙ neutron stars, and generate neutron star radii below 13 km. Making use of these equations of state, cooling simulations for isolated neutron stars are performed. We find that two of the models studied, FSU2R (with nucleons) and, in particular, FSU2H (with nucleons and hyperons), show very good agreement with cooling observations, even without including nucleon pairing. This indicates that cooling observations are compatible with an equation of state that produces a soft nuclear symmetry energy and, thus, generates small neutron star radii. Nevertheless, both schemes produce cold isolated neutron stars with masses above 1.8M_⊙.

Recent trends in processor power for the next generation devices point clearly to significant increase in processor heat dissipation over the coming years. In the desktop system design space, the tendency has been to minimize system enclosure size while maximizing performance, which in turn leads to high power densities in future generation systems. The current thermal solutions used today consist of advanced heat sink designs and heat pipe designs with forced air cooling to cool high power processors. However, these techniques are already reaching their limits to handle high heat flux, and there is a strong need for development of more efficient cooling systems which are scalable to handle the high heat flux generated by the future products.

To meet this challenge, there has been research in academia and in industry to explore alternative methods for extracting heat from high-density power sources in electronic systems. This talk will discuss the issues surrounding device cooling, from the transistor level to the system level, and describe system-level solutions being developed for desktop computer applications developed in our group at Stanford University.

Muon colliders and neutrino factories are attractive options for achieving the highest lepton-antilepton collision energies and the most precise measurements of the parameters of the neutrino mixing matrix. The performance and cost of these future facilities depends sensitively on how well a beam of muons can be cooled. The recent progress of muon-cooling prototype tests and design studies nourishes the hope that such facilities can be built during the next decade.

We discuss how the present uncertainty in the pairing properties of neutron matter affects the thermal response of the inner crust of neutron star in the case of a rapid cooling process. It is shown that the thermalisation time of the inner crust is changing by a factor of two if in the calculations one shifts between two posible pairing scenarios for neutron superfluidity, i.e., one corresponding to the BCS approximation and the other to many-body techniques which include polarisation effects.

We investigate the thermal evolution of isolated neutron stars, including the transition of nuclear matter into quark matter at some time during the cooling stage. We show cooling curves by changing the transition periods in parametric manner. If there would be observational data which fit to our results, it suggests the existence of quark stars.

The parity doublet model, containing the SU(2) multiplets including the baryons identified as the chiral partners of the nucleons is applied to neutron stars. The maximum mass for the star is calculated for different stages of the cooling taking into account finite temperature/entropy effect, trapped neutrinos and fixed baryon number. Rotation effects are also included.

Superconducting devices such as magnets and cavities are key components in the accelerator field for increasing the beam energy and intensity, and at the same time making the system compact and saving on power consumption in operation. An effective cryogenic system is required to cool and keep the superconducting devices in the superconducting state stably and economically. The helium refrigeration system for application to accelerators will be discussed in this review article. The concept of two cooling modes — the liquefier and refrigerator modes — will be discussed in detail because of its importance for realizing efficient cooling and stable operation of the system. As an example of the practical cryogenic system, the TRISTAN cryogenic system of KEK Laboratory will be treated in detail and the main components of the cryogenic system, including the high-performance multichannel transfer line and liquid nitrogen circulation system at 80K, will also be discussed. In addition, we will discuss the operation of the cryogenic system, including the quench control and safety of the system. The satellite refrigeration system will be discussed because of its potential for wide application in medium-size accelerators and in industry.

Micro channel cooling is considered to be a promising technique to cool high energy physics detectors in the future. Especially tracking detectors will need to minimize the material crossed by particles to comply with future physics demands. The flexibility of micro-fabrication processes and the high thermal efficiency, due to the large heat exchange surface allows the production of efficient heat sinks, well adapted to the needs of different detectors. As a first HEP application, the NA62 GTK silicon pixel detector will use micro channel cooling. A low temperature fluid circulates in a micro-fabricated silicon heat sink, locally thinned to 130 μm in the sensitive area of the detector.