Effect of Barrier Thickness and Height on the Transmission Coefficient of GaAs/Ga1–xAlxAs Quantum Cascaded Laser (QCL)

2020 ◽  
Vol 12 (1) ◽  
pp. 95-99
Author(s):  
Manish Kumar Yadav ◽  
Bramha P. Pandey ◽  
Dharmendra Kumar
Keyword(s):  
Transmission Coefficient ◽  
Barrier Height ◽  
Electron Tunneling ◽  
Operating Temperature ◽  
Measurable Quantity ◽  
Barrier Thickness ◽  
Lower Temperature ◽  
The Impact

This paper demonstrates the impact of barrier thickness on the transmission coefficient of GaAs/Ga1–xAlxAs quantum cascaded laser (QCL). The transmission coefficient is the important measurable quantity to predict the properties of quantum cascaded laser (QCL). This paper also includes the effects of the change in composition 'x' of the barrier height on transmission coefficient. In this study, GaAs/Ga1–xAlxAs QCL structures have been selected with operating temperature at T = 10 K. The calculated results show that at lower temperature when the thickness of barrier is less, the probability of electron tunneling is high, therefore, transmission coefficient is high. When we increase the barrier height it results in lowering the probability of electron tunneling, hence transmission coefficient is decreases. The calculated results justified the reported results of other workers.

Truck Tire Operating Temperatures on Flat and Curved Test Surfaces

2005 ◽  
Vol 33 (3) ◽  
pp. 156-178 ◽  
Author(s):  
T. J. LaClair ◽  
C. Zarak
Keyword(s):  
Flat Surface ◽  
Operating Temperature ◽  
Operating Conditions ◽  
Load Pressure ◽  
Truck Tire ◽  
Endurance Testing ◽  
Operating Temperatures ◽  
The Impact ◽  
Tread Rubber ◽  
Cylindrical Test

Abstract Operating temperature is critical to the endurance life of a tire. Fundamental differences between operations of a tire on a flat surface, as experienced in normal highway use, and on a cylindrical test drum may result in a substantially higher tire temperature in the latter case. Nonetheless, cylindrical road wheels are widely used in the industry for tire endurance testing. This paper discusses the important effects of surface curvature on truck tire endurance testing and highlights the impact that curvature has on tire operating temperature. Temperature measurements made during testing on flat and curved surfaces under a range of load, pressure and speed conditions are presented. New tires and re-treaded tires of the same casing construction were evaluated to determine the effect that the tread rubber and pattern have on operating temperatures on the flat and curved test surfaces. The results of this study are used to suggest conditions on a road wheel that provide highway-equivalent operating conditions for truck tire endurance testing.

Расчетные методы оценки ударной вязкости сварных элементов с трещинами

2020 ◽  
Vol 44 (3) ◽  
pp. 22-36
Author(s):  
Keyword(s):  
Stress Intensity ◽  
Impact Strength ◽  
Welded Joints ◽  
Development Process ◽  
Welded Joint ◽  
Operating Temperature ◽  
Crack Development ◽  
Heterogeneous Structure ◽  
Critical Crack Length ◽  
The Impact

Практика показывает, что для сварных конструкций, эксплуатируемых в условиях Крайнего Севера необходимо уделять внимание работоспособности сварных соединений при низких температурах. Металл сварных соединений в процессе воздействия обработки изменяет свои свойства, снижается ударная вязкость, образуется гетерогенная структура с большой степенью разнозернистости. Чтобы оценивать и иметь возможность правильно контролировать термическое воздействие и последствия сварочного процесса, требуется решить задачу аналитического определения ударной вязкости для всех зон сварного соединения. В настоящей статье представлен инженерный метод оценки ударной вязкости, применимый для любой зоны сварного соединения, в которой имеется острый или особый концентратор напряжений – трещина. Разработанный аналитический метод расчета ударной вязкости отражает качественную и количественную картину взаимосвязи структурно-механических характеристик и работы развития трещины в диапазоне температур 77…300 К. Предложенная схематизация зависимости критического коэффициента интенсивности напряжений от температуры позволила найти коэффициенты, характеризующие свойства материала, и выполнить расчеты изменения предела текучести и предела прочности от температуры эксплуатации. Построены графики зависимости работы развития трещины от температуры эксплуатации для сталей 15ГС и 17ГС, сравнение которых с экспериментальными данными показывает удовлетворительное согласование. Найдено, что при напряжениях предела выносливости отношение работы развития трещины к критической длине трещины постоянно, не зависит от температуры и для сталей 15ГС и 17ГС равно около 10. Ключевые слова: ударная вязкость, работа разрушения, коэффициент интенсивности напряжений, трещина, феррито-перлитная сталь, зона термического влияния. For welded structures under operation in the Far North, attention must be paid to the performance of welded joints at low temperatures. The properties of metal of welded joints are changed in the process of treatment, its toughness decreases, and a heterogeneous structure with a large range of different grain sizes is formed. In order to evaluate and be able to correctly control the thermal effect and the consequences of the welding process, it is necessary to solve the problem of analytical determination of impact strength for all zones of the welded joint. The paper presents an engineering method for evaluation of the impact strength applicable to any area of the welded joint in which there is a sharp or super sharp stress concentrator – a crack. The developed analytical method for calculating the impact strength reflects a qualitative and quantitative codependency of structural and mechanical characteristics and the process of crack development in the temperature range of 77–300 K. The proposed schematization of dependence of the critical coefficient of stress intensity on the temperature made it possible to find coefficients characterizing the properties of the material and to perform calculations of changes in yield strength and tensile strength on operating temperature. Graphs of the crack development process dependency on the operating temperature for 15ГС and 17ГС steels were constructed, and their comparison with experimental data displays satisfactory agreement. It was found that at endurance limit stresses, the ratio of the crack development process to the critical crack length is constant, non-dependent on temperature, and is equal to 10 for 15ГС and 17ГС steels. Keywords: impact strength, fracture work, stress intensity factor, crack, ferrite-pearlite steel, heat affected zone, steel tempering.

Comparative Analysis of Autoxidation of Haemoglobin

2001 ◽  
Vol 204 (11) ◽  
pp. 2029-2033
Author(s):  
Frank B. Jensen
Keyword(s):  
Temperature Sensitivity ◽  
Oxidation Rate ◽  
Protective Role ◽  
Yellowfin Tuna ◽  
Histidine Residue ◽  
River Lamprey ◽  
Different Temperatures ◽  
Lower Temperature ◽  
The Impact

SUMMARY Autoxidation of oxyhaemoglobin (oxyHb) to methaemoglobin was measured at different temperatures in haemoglobin solutions from Atlantic hagfish, river lamprey, common carp, yellowfin tuna and pig. The aims were to evaluate the impact of the absent distal histidine in hagfish haemoglobin, the importance of oxyHb being either monomeric (hagfish and lamprey) or tetrameric (carp, tuna and pig) and to gain information on the temperature-sensitivity of autoxidation. The rate of autoxidation was lower in hagfish than in carp, yellowfin tuna and lamprey haemoglobins at any given temperature. Substitution of the distal histidine residue (His E7) with glutamine in hagfish haemoglobin was therefore not associated with an accelerated autoxidation, as might be expected on the basis of the normal protective role of His E7. Glutamine may have similar qualities to histidine and be involved in the low susceptibility to autoxidation. The low oxidation rate of hagfish haemoglobin, together with an oxidation rate of lamprey haemoglobin that did not differ from that of carp and yellowfin tuna haemoglobins, also revealed that autoxidation was not accelerated in the monomeric oxyhaemoglobins. Pig haemoglobin was oxidised more slowly than fish haemoglobins, demonstrating that fish haemoglobins are more sensitive to autoxidation than mammalian haemoglobins. The rate of autoxidation of hagfish haemoglobin was, however, only significantly greater than that of pig haemoglobin at high temperatures. Autoxidation was accelerated by rising temperature in all haemoglobins. Arrhenius plots of carp and yellowfin tuna haemoglobin revealed a break at 25°C, reflecting a lower temperature-sensitivity between 5 and 25°C than between 25 and 40°C.

scholarly journals An extended grain boundary barrier height model including the impact of internal electric field

AIP Advances ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 115126 ◽  
Author(s):  
Bai-Xiang Xu ◽  
Zi-Qi Zhou ◽  
Peter Keil ◽  
Till Frömling
Keyword(s):  
Grain Boundary ◽  
Electric Field ◽  
Barrier Height ◽  
Internal Electric Field ◽  
The Impact ◽  
Height Model ◽  
Grain Boundary Barrier

scholarly journals Fluctuation Characteristic Test of Oblique Stress Waves in Infilled Jointed Rock and Study of the Analytic Method

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Jin Yu ◽  
Zehan Liu ◽  
Ze He ◽  
Xianqi Zhou ◽  
Jinbi Ye
Keyword(s):  
Transmission Coefficient ◽  
Impact Velocity ◽  
Joint Angle ◽  
Split Hopkinson Pressure Bar ◽  
Strain Curve ◽  
Stress Waves ◽  
Transmitted Wave ◽  
Impact Rate ◽  
Dip Angle ◽  
The Impact

The propagation of stress waves in filled jointed rocks involves two important influencing factors: transmission-reflection phenomena and energy attenuation. In this paper, the split Hopkinson pressure bar (SHPB) test is used to shock the filled rock with joint angles of 0, 30, and 45° and the thickness of 4 mm and 10 mm, respectively, in three different velocities. The wave curves of the incident wave, reflected wave, and transmission are obtained. The effects of the filling angle and joint thickness on wave propagation are analyzed. Based on the propagation characteristics of stress waves in joints, the stress expression of oblique incident stress waves propagating in filling joints is derived, and the energy coefficient of transmission and reflection is calculated. The results show that the propagation of stress wave in filling joints is related to the impact rate. The larger the impact rate is, the larger the maximum voltage amplitude of the three waves is. And the increasing amplitude of the incident and reflected waves is larger than the transmitted wave; the greater the impact velocity is, the smaller the stress-strain curve gap of the three dip joints is, and the fracture strength of the specimen decreases with the increase of the joint dip angle. The larger the joint dip angle is, the smaller the deformation of the rock-like specimen is. The change of the transmission coefficient is related to the joint angle, and the larger joint angle weakens the influence of the joint width on the transmission of the transmitted wave; under each impact velocity, the theoretical and experimental stress peaks are approximately the same, and the transmission coefficient maintains a good consistency with the oblique incident angle.

The impact of barrier height distributions in tunnel junctions

2009 ◽  
Vol 105 (9) ◽  
pp. 094505 ◽  
Author(s):  
Casey W. Miller ◽  
Dustin D. Belyea
Keyword(s):  
Barrier Height ◽  
Tunnel Junctions ◽  
The Impact

The Impact of Hybrid Wet/Dry Cooling on Concentrating Solar Power Plant Performance

2010 ◽  
Author(s):  
Michael J. Wagner ◽  
Charles Kutscher
Keyword(s):  
Solar Power ◽  
Rankine Cycle ◽  
Plant Performance ◽  
Concentrating Solar Power ◽  
Heat Rejection ◽  
Power Block ◽  
Lower Temperature ◽  
Solar Field ◽  
The Impact ◽  
Dry Cooling

This paper examines the sensitivity of Rankine cycle plant performance to dry cooling and hybrid (parallel) wet/dry cooling combinations with the traditional wet-cooled model as a baseline. Plants with a lower temperature thermal resource are more sensitive to fluctuations in cooling conditions, and so the lower temperature parabolic trough plant is analyzed to assess the maximum impact of alternative cooling configurations. While low water-use heat rejection designs are applicable to any technology that utilizes a Rankine steam cycle for power generation, they are of special interest to concentrating solar power (CSP) technologies that are located in arid regions with limited water availability. System performance is evaluated using hourly simulations over the course of a year at Daggett, CA. The scope of the analysis in this paper is limited to the power block and the heat rejection system, excluding the solar field and thermal storage. As such, water used in mirror washing, maintenance, etc., is not included. Thermal energy produced by the solar field is modeled using NREL’s Solar Advisor Model (SAM).

Dynamic Finite Element Analysis of Drum-Type Shipping Packages for Radioactive Materials

2012 ◽  
Author(s):  
Zenghu Han ◽  
Vikram N. Shah ◽  
Yung Y. Liu
Keyword(s):  
Finite Element ◽  
Structural Performance ◽  
Type B ◽  
Regulatory Requirements ◽  
Radioactive Materials ◽  
Structural Evaluation ◽  
Test Conditions ◽  
Physical Testing ◽  
Lower Temperature ◽  
The Impact

The US Department of Energy (DOE) often uses Type AF and Type B drum-type packages for shipment of radioactive materials (RAM), both of which shall be designed and certified to meet the regulatory requirements specified in 10 CFR 71, to ensure safety, public health and protection of environment. In particular for the hypothetical accident conditions (HAC) prescribed in 10 CFR 71.73, RAM packages are subjected to sequential tests of 30-ft drop, crush, puncture, engulfing fire, and water immersions. Packages shall maintain structural integrity of containment, radiation shielding, and criticality control following these HAC tests. The structural evaluation (i.e., drop, crush, and puncture) of packages should address different combinations of test conditions, such as drop orientations, sequence, temperature and payload during the drop, crush and puncture tests. The combinations to be considered are those which would produce most damage to the package, challenge the most vulnerable packaging components, and cause the most cumulative damages. The evaluation of the most damage should also consider the effects of fire and water immersions following the structural tests. In this paper, the structural evaluation details of two drum-type packages, Model 9979 Type AF and Model ES-3100 Type B(U)F, are discussed. The design and performance of these packages were evaluated by physical testing of full-size prototype units. However, it is not practical to account for the worst test conditions and sequence in physical testing. Therefore, confirmatory finite element analyses have been performed to determine whether the cumulative damage resulting from the worst test sequence and conditions is acceptable. It was found for the 9979 package, the corner drop followed by corner crush causes most damage, and most unfavorably challenges its split-ring closures; for the ES-3100 package, the containment vessel (CV) experiences maximum strain following the sequence of bottom-to-lid slapdown and side crush. Although a lower temperature does not compromise their structural performance, the ES-3100 CV does experience slightly more strain because the impact limiter imparts more impact load because of its higher stiffness at lower temperature. In summary, the confirmatory analysis results show that the structural performance of the packages meets the regulatory requirements.

scholarly journals Influence of Fluorine on Clinker burnability and mechanical properties of CPA Moroccan cement

2018 ◽  
Vol 149 ◽  
pp. 01075 ◽  
Author(s):  
A. Bouregba ◽  
A. Diouri ◽  
B. Elghattas ◽  
A. Boukhari ◽  
T. Guedira
Keyword(s):  
Mechanical Properties ◽  
Fluorescence Spectroscopy ◽  
Calcium Fluoride ◽  
X Ray Diffraction ◽  
Free Lime ◽  
X Ray ◽  
The Subject ◽  
Lower Temperature ◽  
The Impact ◽  
Cement Raw Mix

It has been found that the addition of certain components, despite their low concentration in raw mix, may accelerate and enhance the reactivity of the cement raw mix. The utilization of mineralizers to facilitate and quicken the process of clinkerization backpedals numerous years, the concept of using such mineralizers to burn normal raw mixes at a much lower temperature with the end goal of decreasing the fuel necessities of the furnace and to enhance the cement proprieties has become to be seriously considered over the most recent couple of years. The subject of this paper is to investigate the impact of calcium fluoride as mineralizer on addition during the clinkerization process of industrial raw mixtures and its effect on chemical, mineralogical, and mechanical properties of CPA Moroccan cement. Five different raw meals were utilized and were burned with 2% of calcium fluoride. The resulting clinker was analyzed by X-ray diffraction (XRD) and fluorescence spectroscopy to determine the chemical phases of the obtained clinker, and the mechanical properties of resulting CPA cement were determined. The results show that the addition of 2% of CaF2 to the clinker raw meal induced a decrease in the burning temperature and free lime, while improving the clinker phase formation and the mechanical properties of obtained cement.

Comparison of channel mobility and oxide properties of MOSFET devices on Si-face (0001) and A-face (11-20) 4H-SiC

2014 ◽  
Vol 1693 ◽  
Author(s):  
Daniel J. Lichtenwalner ◽  
Lin Cheng ◽  
Scott Allen ◽  
John W. Palmour ◽  
Aivars Lelis ◽  
...  
Keyword(s):  
Valence Band ◽  
Barrier Height ◽  
Field Effect ◽  
Phonon Scattering ◽  
Electron Tunneling ◽  
Negative Temperature ◽  
Field Effect Mobility ◽  
Channel Mobility ◽  
P Type ◽  
And Control

ABSTRACTIn this report we present results comparing lateral MOSFET properties of devices fabricated on Si-face (0001) and A-face (11-20) 4H-SiC, with nitric oxide passivation anneals. We observe a field-effect mobility of 33 cm2/V.s on p-type 5×1015 doped Si-face. These devices have a peak field-effect mobility which increases with temperature, indicative of a channel mobility limited by coulomb scattering. On 1×1016 p-type A-face SiC, the peak channel mobility is observed to be 80 cm2/V.s, with a negative temperature dependence, indicating that phonon-scattering effects dominate, with a much lower density of shallow acceptor traps. This > 2x higher channel mobility would result in a substantial decrease in on-resistance, hence lower power losses, for 4H-SiC power MOSFETs with voltage ratings below 2 kV. However, MOS C-V and gate leakage measurements indicate very different oxide and interface quality on each SiC face. For example, the Fowler-Nordheim (FN) conduction-band (CB) barrier height for electron tunneling at the SiO2/SiC interface is 2.8 eV on Si-face SiC, while it is 2.5 eV or less on A-face SiC. For the valence-band side, the effective FN barrier height at the valence-band (VB) side of only 1.6 eV on A-face SiC, while the VB barrier height is about 3.1 eV on Si-face SiC. Moreover, C-V of the MOS gate on A-face indicates the presence of a high-density of deep hole traps. It is apparent that oxides on alternative crystal faces, very promising in terms of channel mobility, require further study for complete understanding and control of the interface properties.

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