good thermal contact
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2021 ◽  
Author(s):  
Dillon McClintock ◽  
Neil T. Wright

Abstract Cryolipolysis is a noninvasive clinical procedure for the local reduction of adipose tissue. Paddles as cold as ~10 °C are placed in good thermal contact the epidermis. The goal is to cool the subcutaneous adipose tissue to ~10 °C, which induces apoptosis and an inflammatory response in the adipocytes. The dermis is, of course, cooler than the adipocytes, but the triglyceride in the adipocytes are thought to crystalize, causing apoptosis. The clinical procedure have been developed empirically. A mathematical model could aid in understanding the mechanisms of response and improving the design of the procedure. Here, the Pennes equation is used to model the temperature of the tissue during cooling. The two parameters identified are the thermal diffusivity of the tissue and a blood perfusion parameter, which also gives the characteristic length. Green's functions are used to solve the Pennes equation, which simplifies to a transient fin equation.


Electronics ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 1410
Author(s):  
Piotr Marek Markowski ◽  
Mirosław Gierczak ◽  
Andrzej Dziedzic

The monitoring of processor temperature is crucial to increase its efficiency. One of the novel approaches is use the information not only about the CPU (Central Processing Unit) thermal state, but also about changing environmental conditions. The additional temperature difference sensor to monitor thermal changes in the processor environment is necessary. The sensor dedicated for active heat sink, often used inside laptops, was designed, fabricated and investigated. To fulfill the requirements and to match to the specific shape of the active heat sink, the hybrid sensor was proposed. It was composed of six thermocouples and fabricated using thick-film and LTCC (Low Temperature Cofired Ceramic) technology combined with wire thermocouples. Thick-film/LTCC flat substrates with thermoelectric paths ensured good thermal contact between the sensor and the monitored surface. The thermoelectric wires allowed adjusting the sensor to the complicated shape of the active heatsink. Three different versions of the sensor were realized and compared. All of them seem to be suitable for measuring the temperature difference in the given application and they can be used in further works.


2020 ◽  
Vol 6 (18) ◽  
pp. eaaz6986
Author(s):  
Daniela Pagliero ◽  
Pablo R. Zangara ◽  
Jacob Henshaw ◽  
Ashok Ajoy ◽  
Rodolfo H. Acosta ◽  
...  

Disorder and many body interactions are known to impact transport and thermalization in competing ways, with the dominance of one or the other giving rise to fundamentally different dynamical phases. Here we investigate the spin diffusion dynamics of 13C in diamond, which we dynamically polarize at room temperature via optical spin pumping of engineered color centers. We focus on low-abundance, strongly hyperfine-coupled nuclei, whose role in the polarization transport we expose through the integrated impact of variable radio-frequency excitation on the observable bulk 13C magnetic resonance signal. Unexpectedly, we find good thermal contact throughout the nuclear spin bath, virtually independent of the hyperfine coupling strength, which we attribute to effective carbon-carbon interactions mediated by the electronic spin ensemble. In particular, observations across the full range of hyperfine couplings indicate the nuclear spin diffusion constant takes values up to two orders of magnitude greater than that expected from homo-nuclear spin couplings.


2015 ◽  
Vol 2015 ◽  
pp. 1-19 ◽  
Author(s):  
Marcel Miglierini ◽  
Mariusz Hasiak

Structural modifications and their impact upon magnetic properties are studied in amorphous and nanocrystalline NANOPERM-type57Fe75Mo8Cu1B16alloy. They are introduced by irradiation with 130 keV N+ions to the total fluencies of up to 2.5 × 1017 ions/cm2under different cooling conditions. Increased temperature during the irradiation triggers formation of nanocrystallites of bcc-Fe in those subsurface regions that are affected by bombarding ions. No crystallization occurs when good thermal contact between the irradiated sample and a sample holder is assured. Instead, structural rearrangement which favours development of magnetically active regions was determined by the local probe methods of Mössbauer spectrometry. Dipole magnetic interactions dominate in subsurface regions on that side of the ribbons which was exposed to ion irradiation. Nevertheless, structural modifications demonstrate themselves also via macroscopic magnetic parameters such as temperature dependence of magnetization, Curie temperature, and hysteresis loops. Impact of only the temperature itself to the observed effects is assessed by the help of samples that were subjected just to heat treatment, that is, without ion irradiation.


Author(s):  
Danie`le Fournier ◽  
Jean Paul Roger ◽  
Christian Fretigny

Lateral heat diffusion thermoreflectance is a very powerful tool for determining directly the thermal diffusivity of layered structures. To do that, experimental data are fitted with the help of a heat diffusion model in which the ratio between the thermal conductivity k and the thermal diffusivity D of each layer is fixed, and the thermal properties of the substrate are known. We have shown in a previous work that it is possible to determine independently the thermal diffusivity and the thermal conductivity of a metallic layer deposited on an insulator, by taking into consideration all the data obtained at different modulation frequencies. Moreover, it is well known that to prevent a lack of adhesion of a gold film deposited on substrates like silica, an intermediate very thin (Cr or Ti) layer is deposited to assure a good thermal contact. We extend our previous work: the asymptotic behaviour determination of the surface temperature wave at large distances from the modulated point heat source for one layer deposited on the substrate to the two layers model. In this case (very thin adhesion coating whose thermal properties and thickness are known), it can be establish that the thermal diffusivity and the thermal conductivity of the top layer can still be determined independently. It is interesting to underline that the calculus can also be extended to the case of a thermal contact resistance which has often to be taken into account between two solids. We call thermal resistance a very thin layer exhibiting a very low thermal conductivity. In this case, the three parameters we have to determine are the thermal conductivity and the thermal diffusivity of the layer and the thermal resistance. We will show that, in this case, the thermal conductivity of the layer is always obtained independently of a bound of the couple thermal resistance – thermal diffusivity, the thermal diffusivity being under bounded and the thermal resistance lower bounded. Experimental results on thin gold layers deposited on silica with and without adhesion layers are presented to illustrate the method. Discussions on the accuracy will also be presented.


1998 ◽  
Vol 518 ◽  
Author(s):  
H. Tada ◽  
A. R. Abramson ◽  
P. Nieva ◽  
P. Zavracky ◽  
I. N. Miaoulis ◽  
...  

AbstractIn high temperature processing of microelectronics such as rapid thermal processing (RTP), an accurate measurement of temperature is critical in fabricating defect-free devices. Currently, temperatures during such processes are measured using thermocouples or pyrometers. However, accurate measurements with thermocouples are troublesome due to the difficulties in holding the thermocouples in place and maintaining good thermal contact. A further drawback for thermocouples is that they are highly intrusive. For pyrometers, optical interference effects and partial transparency limit their applicability and the local temperature of wafers near the electronic devices are difficult to measure using pyrometer due to relatively large spot size. Microelectromechanical systems (MEMS) technology is being used in developing innovative temperature sensor (T-MEMS), which allow an ex-situ examination of the maximum temperature reached during a thermal process by creating a permanent change in structure at high temperatures. The performance of the device relies on the thermophysical properties of the materials; specifically, the Young's modulus, thermal expansion coefficient, and the ultimate strength must be considered for silicon, and silicon nitride. Through careful experimental design and accurate modeling of their structural behavior, the high-temperature material properties can be determined using the T-MEMS and calibrated furnaces.


1993 ◽  
Vol 303 ◽  
Author(s):  
Marlio J. C. Bonfim ◽  
Jacobus W. Swart ◽  
Cristian E. M. Velasco ◽  
Juscelino H. Okura ◽  
Patrick B. Verdonck

ABSTRACTA multiprocess CVD system with the following main features is designed and constructed: the wafer holder is made of a Si wafer with diameter larger than the process wafers. This larger holder produces a better temperature uniformity on the process wafer. A good thermal contact between holder and process wafer is obtained by an electrostatic clamp. The holder supports the process wafer facing down. A remote plasma is produced in a small chamber inside the process chamber. The 100 KHz RF frequency keeps the system very simple and cheap while still reasonable ionization is achieved. SiO2 films were deposited using SiH4 and O2 with and without remote plasma of O2. At low temperatures and 1.5 Torr, process activation energies of about 0.9 and 0.3 eV were obtained respectively.


1992 ◽  
Vol 36 ◽  
pp. 403-410 ◽  
Author(s):  
R. Ebner ◽  
M. Mantler ◽  
F. Weber

A prototype of a new high temperature chamber has been developed at our institute. Like most of such chambers it has an evacuated housing which is watercooled, and in its center a tungsten heating strip is mounted on watercooled clamps (fig.1). A special way of clamping compensates for thermal expansion automatically and thus keeps the specimen in an aligned position. The specimen is mounted directly onto the heating strip's surface. Specimens are prepared using fine powders mixed with distilled water and acetone to give a thin slurry. This mixture is put onto the heating strip and carefully dried with a heatgun. This way of preparing a specimen makes it cling to the heating strip quite well even at temperatures above 3000K and therefore provides good thermal contact.


Geophysics ◽  
1986 ◽  
Vol 51 (8) ◽  
pp. 1580-1584 ◽  
Author(s):  
Tien‐Chang Lee ◽  
Thomas L. Henyey ◽  
Brian N. Damiata

We present a method for absolute measurement of thermal conductivity of drill cuttings. The simplicity of the apparatus makes it suitable for nondestructive use of cuttings and for sample sizes too small to be measured with a needle probe. Because the measurement is absolute, no calibration standards are required. Samples are placed in a Plexiglas cup with a lid containing an electric heat source. The base of the cup is placed in good thermal contact with an aluminum‐block heat sink. Upward and radial heat losses are minimized with styrofoam insulation surrounding the cup. The accuracy of the method was estimated by cross‐measurement of selected samples with a well‐calibrated needle probe. Results indicate that errors in measurement are less than 5 percent for sample conductivities greater than 0.8 W/m ⋅ K if the heat loss through the styrofoam insulation is accounted for. Reproducibility is typically within 3 percent. An axisymmetric finite‐element model which simulates the temperature distribution of the measurement apparatus further demonstrates its viability.


1986 ◽  
Vol 40 (5) ◽  
pp. 588-595 ◽  
Author(s):  
Robert H. Hauge ◽  
Leif Fredin ◽  
Zakya H. Kafafi ◽  
John L. Margrave

A multisurface matrix-isolation apparatus has been designed and interfaced to an FT-IR vacuum spectrometer. The design permits independent matrix-isolation studies with sixty different surfaces. It also allows direct measurement of matrix gas to guest ratios with an integral cooled quartz crystal microbalance. Problems associated with moving the matrix block while maintaining good thermal contact are discussed. Finally, some applications to studies of coal pyrolysis, metal atom chemistry, and quantitative analysis are presented.


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