A Reexamination of Phonon Transport Through a Nanoscale Point Contact in Vacuum

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Michael Thompson Pettes ◽  
Li Shi
Keyword(s):  
Contact Area ◽  
Room Temperature ◽  
Near Field ◽  
Point Contact ◽  
Thermal Conductance ◽  
Phonon Transport ◽  
Interfacial Resistance ◽  
Resistance Thermometer ◽  
Measurement Results ◽  
Interface Contact

Using a silicon nitride cantilever with an integral silicon tip and a microfabricated platinum–carbon resistance thermometer located close to the tip, a method is developed to concurrently measure both the heat transfer through and adhesion energy of a nanoscale point contact formed between the sharp silicon tip and a silicon substrate in an ultrahigh vacuum atomic force microscope at near room temperature. Several models are used to evaluate the contact area critical for interpreting the interfacial resistance. Near field-thermal radiation conductance was found to be negligible compared to the measured interface thermal conductance determined based on the possible contact area range. If the largest possible contact area is assumed, the obtained thermal interface contact resistance can be explained by a nanoconstriction model that allows the transmission of phonons from the whole Brillouin zone of bulk Si with an average finite transmissivity larger than 0.125. In addition, an examination of the quantum thermal conductance expression suggests the inaccuracy of such a model for explaining measurement results obtained at above room temperature.

Experimental Investigation of Thermal Transport Mechanisms Through a Nanoscale Point Contact

2011 ◽  
Author(s):  
Michael Thompson Pettes ◽  
Li Shi
Keyword(s):  
Radiation Transport ◽  
Thermal Contact ◽  
Near Field ◽  
Temperature Drop ◽  
Point Contact ◽  
Dominant Mode ◽  
Large Temperature ◽  
Resistance Thermometer ◽  
Atomic Force ◽  
Field Radiation

Using a silicon nitride cantilever with an integral Si tip and a micro-fabricated Pt-C resistance thermometer placed close to the tip, we have measured the thermal contact resistance of a nanoscale Si point contact in an ultrahigh vacuum atomic force microscope at near room temperature. The temperature of the cantilever tip was observed to remain constant during approach to, while in contact with, and during retraction from the Si substrate, while a large temperature drop was observed at the points of contact and separation, suggesting negligible near-field radiation transport in the experiment reported here. Detailed contact mechanics calculations of the contact diameter and modeling of the nanocontact show that solid-solid conduction with phonon transmission coefficient of at least 0.12 is the dominant mode of heat transfer through the nanoscale contact.

Thermal Conductivity Measurement of Graphene Exfoliated on Silicon Dioxide

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
Jae Hun Seol ◽  
Arden L. Moore ◽  
Li Shi ◽  
Insun Jo ◽  
Zhen Yao
Keyword(s):  
Thermal Conductivity ◽  
Silicon Dioxide ◽  
Ultrathin Films ◽  
Room Temperature ◽  
Electronic Materials ◽  
Conductivity Measurement ◽  
Thermal Conductivity Measurement ◽  
Resistance Thermometer ◽  
Numerical Heat Transfer ◽  
Measurement Results

We have developed a nanofabricated resistance thermometer device to measure the thermal conductivity of graphene monolayers exfoliated onto silicon dioxide. The measurement results show that the thermal conductivity of the supported graphene is approximately 600 W/m K at room temperature. While this value is lower than the reported basal plane values for graphite and suspended graphene because of phonon leakage across the graphene-support interface, it is still considerably higher than the values for common thin film electronic materials. Here, we present a detailed discussion of the design and fabrication of the measurement device. Analytical and numerical heat transfer solutions are developed to evaluate the accuracy and uncertainty of this method for thermal conductivity measurement of high-thermal conductivity ultrathin films.

Magnetic and phonon transport properties of two-dimensional room-temperature ferromagnet VSe2

2021 ◽  
Author(s):  
Haohao Sheng ◽  
Haoxiang Long ◽  
Guanzhen Zou ◽  
Dongmei Bai ◽  
Junting Zhang ◽  
...  
Keyword(s):  
Transport Properties ◽  
Room Temperature ◽  
Phonon Transport ◽  
Two Dimensional

scholarly journals Multi-Probe Measurement System Based on Single-Cut Transformation for Fast Testing of Linear Arrays

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1744
Author(s):  
Fernando Rodríguez Varela ◽  
Manuel José López Morales ◽  
Rubén Tena Sánchez ◽  
Alfonso Tomás Muriel Barrado ◽  
Elena de la Fuente González ◽  
...  
Keyword(s):  
Measurement System ◽  
Near Field ◽  
Linear Measurement ◽  
Complete Characterization ◽  
Linear Arrays ◽  
Full Characterization ◽  
X Band ◽  
Measurement Results ◽  
The Many ◽  
3D Information

This paper introduces a near-field measurement system concept for the fast testing of linear arrays suited for mass production scenarios where a high number of nominally identical antennas needs to be measured. The proposed system can compute the radiation pattern, directivity and gain on the array plane, as well as the array complex feeding coefficients in a matter of seconds. The concept is based on a multi-probe antenna array arranged in a line which measures the near field of the antenna under test in its array plane. This linear measurement is postprocessed with state-of-the-art single-cut transformation techniques. To compensate the lack of full 3D information, a previous complete characterization of a “Gold Antenna” is performed. This antenna is nominally identical to the many ones that will be measured with the proposed system. Therefore, the data extracted from this full characterization can be used to complement the postprocessing steps of the single-cut measurements. An X-band 16-probe demonstrator of the proposed system is implemented and introduced in this paper, explaining all the details of its architecture and operation steps. Finally, some measurement results are given to compare the developed demonstrator with traditional anechoic measurements, and show the potential capabilities of the proposed concept to perform fast and reliable measurements.

Experimental and numerical study on cavitation under elastohydrodynamic lubrication point contact

2021 ◽  
pp. 135065012110527
Author(s):  
Mingfei Ma ◽  
Wen Wang ◽  
Wenxun Jiang
Keyword(s):  
Contact Area ◽  
Numerical Study ◽  
Ambient Pressure ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hertzian Contact ◽  
Pressure Area ◽  
Cavitation Pressure ◽  
Experimental Researches ◽  
State 1

As a common phenomenon in elastohydrodynamic lubrication, cavitation has an effect on the completeness of the oil film in the contact area. Many studies have therefore been conducted on cavitation. Experimental researches on cavitation usually rely on optical interference observation, which offers a limited resolution and observation range. In this paper, an infrared thermal camera is used to observe the cavity bubbles on a ball-on-disc setup under sliding/rolling conditions. The results show that the cavity length increases with an increases of the entrainment speed and the viscosity of the lubricants. These observations are explained by a numerical model based on Elrod's algorithm. Effects of entrainment speed and lubricant viscosity on the breakup of cavitation bubbles and the cavitation states are investigated. Both the simulation and experimental results show that a negative pressure area is present behind the Hertzian contact area. The ambient pressure plays a role in maintaining cavitation state 1. The cavitation pressure is close to the vacuum pressure when the entrainment speed is low and to the ambient pressure instead when the entrainment speed is high.

scholarly journals Diameter and Length Effect on Diffusive-Ballistic Phonon Transport in a Carbon Nanotube

2007 ◽  
Author(s):  
Junichiro Shiomi ◽  
Shigeo Maruyama
Keyword(s):  
Thermal Conductivity ◽  
Room Temperature ◽  
Single Walled Carbon Nanotubes ◽  
Phonon Transport ◽  
Boundary Resistance ◽  
Gradual Transition ◽  
Length Effect ◽  
Control Techniques ◽  
Non Equilibrium Molecular Dynamics ◽  
Walled Carbon Nanotubes

We report a non-equilibrium molecular dynamics (MD) study on heat conduction of finite-length single-walled carbon nanotubes (SWNTs). The length and diameter dependences of the thermal conductivity are quantified for a range of nanotube-lengths up to a micrometer at room temperature using two different temperature control techniques. A thorough investigation was carried out on the influence of intrinsic thermal boundary resistance between the temperature-controlled layers and the rest of the SWNT. The trend of length effect indicates a gradual transition from nearly pure ballistic phonon transport to diffusive-ballistic phonon transport. The nearly pure ballistic phonon transport was also confirmed by the minor diameter-dependence of thermal conductivity for short SWNTs. For longer SWNTs with stronger diffusive effect, the thermal conductivity is larger for SWNTs with smaller diameters.

scholarly journals ANALISIS CAPACITY CONSTRAINED WORKER DENGAN PENDEKATAN WAKTU BAKU, DENYUT JANTUNG DAN PROFILE OF MOOD STATES (STUDI KASUS PADA INDUSTRI TEMPE “MUCHLAR”KASIHAN BANTUL)

2014 ◽  
Vol 34 (03) ◽  
pp. 322
Author(s):  
Maman Zuriwiatma ◽  
Mirwan Ushada ◽  
Guntarti Tatik Mulyati
Keyword(s):  
Room Temperature ◽  
Buffer Management ◽  
Mood States ◽  
Working Environment ◽  
Profile Of Mood States ◽  
Standard Time ◽  
Measurement Results ◽  
Capacity Constrained ◽  
Potential Food ◽  
Production Target

Tempe ”Muchlar” is one the potential food indutry which all the job is pursued manually. The production process is based on the worker capacity. The main problem is the industry could not fulfi ll the production target of half-finished Tempe product of + 3.600 kg.  The research objective is to identify Capacity Constrained Worker using standard time, heart rate, profi le of mood states and recommending the improvement to increase the worker capacity. The measurement results were confi rmed using analysis of working environment. The research results indicated that Capacity Constrained Worker of Tempe Industry was the worker of peeling. It was indicated by the standard time of 5,63 detik/kg that could not fulfi ll the production target of 3.600 kg in 5 work hours. The improvement was pursued by decreasing the room temperature of working station. The improvement could increase the standard time of 5 second/kg, fulfi lling the production target and increasing the income. Finally the improvement using Buffer Management could improve the Capacity Constrained Worker in Tempe Industry “Muchlar”.Keywords: Standard time, Capacity Constrained Worker, production target ABSTRAKTempe ”Muchlar” merupakan salah satu industri pangan yang semua pekerjaannya dilakukan manual sehingga proses  produksinya sangat tergantung kapasitas dari pekerja. Permasalahan muncul karena target produksi tempe setengah jadi sebesar + 3.600 kg tidak tercapai.  Penelitian ini bertujuan untuk mengidentifi kasi Capacity Constrained Worker yang terjadi menggunakan pendekatan waktu baku, denyut jantung, profile of mood states serta menentukan perbaikan yang tepat untuk dapat meningkatkan kapasitasnya. Hasil pengukuran terhadap pekerja dikonfi rmasi dengan analisis keadaan lingkungan kerja. Dari hasil penelitian dapat ditentukan bahwa pekerja yang menjadi Capacity Constrained Worker adalah pekerja stasiun pemisahan kulit. Hal ini dibuktikan dari waktu baku yang diperoleh sebesar 5,63 detik/kg yang membuat target produksi sebesar 3.600 kg dalam 5 jam tidak tercapai. Dengan perbaikan yang dilakukan yaitu menurunkan suhu ruangan dari tinggi ke normal waktu baku pekerja dapat meningkat menjadi 5 detik/kg dan target produksi dapat tercapai serta meningkatkan pendapatan. Perbaikan dengan menerapkan buffer management dapat mengurangi stasiun kerja yang menjadi constraint. Kata kunci: Waktu baku, Capacity Constrained Worker, target produksi

scholarly journals Near-Field Antenna Measurements with Manual Collection of the Measurement Samples

2020 ◽  
Vol 18 ◽  
pp. 17-22
Author(s):  
Fabian T. Faul ◽  
Hans-Jürgen Steiner ◽  
Thomas F. Eibert
Keyword(s):  
Near Field ◽  
Field Measurements ◽  
Controlled Environment ◽  
Positioning System ◽  
Probe Position ◽  
Site Testing ◽  
Error Level ◽  
Measurement Results ◽  
Anechoic Chambers ◽  
Chamber Measurements

Abstract. Near-field measurements are commonly performed in anechoic chambers which limits the flexibility of the measurements and requires high precision equipment to achieve exact results. In this contribution, we investigate a simple near-field measurement setup which does not use any sophisticated positioning system nor operates in a controlled environment. Instead, the probe antenna is moved by an operator person while the probe position is measured by a laser tracker. This implies that the measurement results will have a higher error level in comparison with antenna chamber measurements. However, excellent error levels are not always necessary, especially when it comes to on-site testing of the principle functionality of antennas. Measurement results are shown to illustrate the performance of the system.

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