Three-terminal normal-superconductor junction as thermal transistor

We propose a thermal transistor based on a three-terminal normal-superconductor (NS) junction with superconductor terminal acting as the base. The emergence of heat amplification is due to the negative differential thermal conductance (NDTC) effect for the NS diode in which the normal side maintains a higher temperature. The temperature dependent superconducting energy gap is responsible for the NDTC. By controlling quantum dot levels and their coupling strengths to the terminals, a huge heat amplification factor can be achieved. The setup offers an alternative tuning scheme of heat amplification factor and may find use in cryogenic applications.Comment: 6 pages, 3 figure

BASED ON THE STRESS FIELD INTENSITY APPROACH OF PUMPING UNIT HORSE HEAD FATIGUE LIFE PREDICTION

With Nominal Stress Method of pumping unit horse head fatigue life prediction results deviate from the actual,introduction of the Stress Field Intensity Approach,the prediction step of the two methods is given. Based on the cyclic and alternating load analysis of horse head,do static simulation in the ANSYS simulation environment,calculate stress under the ultimate load; do Quasi-static simulation,calculate stress and partial damage regional stress field which changes over time.According to the steps,deal with the simulation results and get the fatigue life prediction of the two kinds of methods. Making count a figure of horse head life and fit the fatigue life distribution to verify accuracy of the two methods,analysis the reason of different result error. The result shows that the Stress Field Intensity Approach forecasting accuracy is higher,predicted result fits the actual

EFFECTS OF DILUTE ACID HYDROLYSIS ON COMPOSITION AND STRUCTURE OF CELLULOSE IN EULALIOPSIS BINATA

Dilute sulfuric acid hydrolysis was performed before the isolation of cellulose from Eulaliopsis binata. And then, the effects of dilute acid hydrolysis on composition and structure of the cellulose was studied in detail. The results indicated that hemicellulose was dissolved mostly and that the lignin-hemicellulose-cellulose interactions were also partially disrupted during the dilute acid hydrolysis. Cellulose in Eulaliopsis binata was identified as the cellulose I allomorph with low crystallinity. What’s more, hydrolysis with dilute acid at high temperature increased the degree of cellulose crystallinity and relatively reduced the proportions of less ordered cellulose allomorphs. This was attributed to a preferential degradation of amorphous cellulose and less ordered crystalline forms during the hydrolysis. The cellulose preparation from Eulaliopsis binata after dilute acid hydrolysis had a higher thermal stability than the cellulose preparation from untreated Eulaliopsis binata

Wafer-level MOCVD growth of AlGaN/GaN-on-Si HEMT structures with ultra-high room temperature 2DEG mobility

In this work, we investigate the influence of growth temperature, impurity concentration, and metal contact structure on the uniformity and two-dimensional electron gas (2DEG) properties of AlGaN/GaN high electron mobility transistor (HEMT) structure grown by metal-organic chemical vapor deposition (MOCVD) on 4-inch Si substrate. High uniformity of 2DEG mobility (standard deviation down to 0.72%) across the radius of the 4-inch wafer has been achieved, and 2DEG mobility up to 1740.3 cm2/V⋅s at room temperature has been realized at low C and O impurity concentrations due to reduced ionized impurity scattering. The 2DEG mobility is further enhanced to 2161.4 cm2/V⋅s which is comparable to the highest value reported to date when the contact structure is switched from a square to a cross pattern due to reduced piezoelectric scattering at lower residual strain. This work provides constructive insights and promising results to the field of wafer-scale fabrication of AlGaN/GaN HEMT on Si