In_xGa_(1-x)N能带结构和Bowing参数的研究

应用总能赝势方法和CASTEP程序对InxGa1-xN进行了模拟计算。利用第一原理密度泛函理论来探讨不含应力的闪锌矿化合物半导体InxGa1-xN在In的不同组分下的带隙值,并利用Veg- ard定理拟合出Bowing参数值为1．5728±0．14783 eV,认为其Bowing值应该在1．5 eV附近。可见InxGa1-xN材料有明显的Bowing现象,这一结果对于InxGa1-xN的异质外延有一定的理论指导作用。

In-situ wafer bowing measurements of GaN grown on Si(111) substrate by reflectivity mapping in metal organic chemical vapor deposition system

In this work, the wafer bowing during growth can be in-situ measured by a reflectivity mapping method in the 3×2 Thomas Swan close coupled showerhead metal organic chemical vapor deposition（MOCVD） system. The reflectivity mapping method is usually used to measure the film thickness and growth rate. The wafer bowing caused by stresses（tensile and compressive） during the epitaxial growth leads to a temperature variation at different positions on the wafer, and the lower growth temperature leads to a faster growth rate and vice versa. Therefore, the wafer bowing can be measured by analyzing the discrepancy of growth rates at different positions on the wafer. Furthermore, the wafer bowings were confirmed by the ex-situ wafer bowing measurement. High-resistivity and low-resistivity Si substrates were used for epitaxial growth. In comparison with low-resistivity Si substrate, Ga N grown on high-resistivity substrate shows a larger wafer bowing caused by the highly compressive stress introduced by compositionally graded Al Ga N buffer layer. This transition of wafer bowing can be clearly in-situ measured by using the reflectivity mapping method.

Theoretical Study on the Origins of the Gap Bowing in Mg_xZn_1–xO Alloys

The full potential linear muffin-tin orbital (FP-LMTO) method was applied to study the structural and electronic properties of the compounds MgO, ZnO and their alloy MgxZn1–xO in the zincblende and NaCl structures. Results are obtained using the local density approximation (LDA), the ground-state properties like lattice constant and bulk modulus obtained agree very well with experimental and other theoretical calculations. The effect of composition on lattice constant from Vegard’s law and the bulk modulus was investigated. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. It is concluded that the energy band gap bowing is primarily due to chemical charge-transfer effect. Contribution of volume deformation and structural relaxation to the gap bowing parameter is found to be very small.

The Bowing Parameters of Ca_χMg_1-χO Ternary Alloys

On the basis of first principles calculations using density functional theory, we explore the structural and electronic properties of two binaries: CaO and MgO in rock salt structures. Structural properties of the semiconductor CaχMg1-χO alloys are derived from total-energy minimization within the General Gradient Approximation. The band gap bowing parameters dependence is very powerful Calcium composition. The results offer that an average bowing parameter of CaχMg1-χO alloys is b = ~0.583$ eV. We analyzed the volume deformation, charge transfer and structural relaxation effects of the CaχMg1-χO alloys.

Blade bowing effects on radial equilibrium of inlet flow in axial compressor cascades

The circumferentially averaged equation of the inlet flow radial equilibrium in axial compressor was deduced. It indicates that the blade inlet radial pressure gradient is closely related to the radial component of the circumferential fluctuation（CF） source item. Several simplified cascades with/without aerodynamic loading were numerically studied to investigate the effects of blade bowing on the inlet flow radial equilibrium. A data reduction program was conducted to obtain the CF source from three-dimensional（3D） simulation results. Flow parameters at the passage inlet were focused on and each term in the radial equilibrium equation was discussed quantitatively. Results indicate that the inviscid blade force is the inducement of the inlet CF due to geometrical asymmetry. Blade bowing induces variation of the inlet CF, thus changes the radial pressure gradient and leads to flow migration before leading edge（LE） in the cascades. Positive bowing drives the inlet flow to migrate from end walls to mid-span and negative bowing turns it to the reverse direction to build a new equilibrium. In addition, comparative studies indicate that the inlet Mach number and blade loading can efficiently impact the effectiveness of blade bowing on radial equilibrium in compressor design.

Effects of blade bowing on the performance of a high pressure-ratio turbocharger centrifugal compressor with self-recirculation casing treatment

The effects of blade bowing on the performance of a high pressure-ratio turbocharger centrifugal compressor were studied by experiments and numerical simulation.The results showed that the negative bowing was capable of increasing the choke mass rate and the efficiency but decreased the surge mass flow rate,while the positive bowing had the opposite effects.When coupling with the self-recirculation casing treatment,the surge mass flow rate of the compressor with negative bowing blade was almost identical with that of the prototype,while the choke mass flow rate was still larger,and the total effect contributed to an increase of the stable flow range by 5.85%at design speed.Besides,the flow mechanism of the coupling effects of blade bowing and self-recirculation casing treatment was discussed.

Intervention of laser periphery iridectomy to posterior iris bowing in high myopic eyes

Background For some high myopic patients with posterior iris bowing, laser periphery iridectomy should be performed pre-operation to prevent pupil block glaucoma if these patients would have phakic intraocular lens implantation to correct high myopia. So we had the opportunity to analysis the influence of laser iridectomy on posterior iris bowing. Methods Eighteen high myopic patients with posterior iris bowing （11 males and 7 females） were involved in the study in Beijing Tongren Eye Center from March 2008 to July 2008. Phakic intraocular lens were implanted to correct their ametropia. The mean age was （32＋6） years （range, 25-40 years）. The center anterior chamber depth, the pupil diameter, the posterior iris bowing depth and the anterior chamber angle were measured with anterior segment coherence tomography （AS-OCT） under the normal condition, myosis condition induced by 2% pilocarpine, laser periphery iridectomy after myosis, and 2% pilocarpine eluting condition respectively. Results There was no significant difference of center anterior chamber depth under the four conditions （P=0.512）. The pupil constricted after pilocarpine （P=0.001）. After＇ laser iridectomy performed and pilocarpine eluted, posterior iris bowing depth reduced more than that in normal condition （P=0.003）. The anterior chamber angle reduced significantly after laser periphery iridectomy and pilocarpine eluted （P=0.012）. Conclusion Laser periphery iridectomy can reduce the posterior iris bowing, which might be due to the change in aqueous circulate pathway.

Hybrid functional calculations on the band gap bowing parameters of In_xGa_(1-x)N

The electronic band structures and band gap bowing parameters of In_xGa_（1-x）N are studied by the firstprinciples method based on the density functional theory. Calculations by employing both the Heyd-ScuseriaErnzerh of hybrid functional（HSE06） and the Perdew-Burke-Ernzerhof（PBE） one are performed. We found that the theoretical band gap bowing parameter is dependent significantly on the calculation method, especially on the exchange-correlation functional employed in the DFT calculations. The band gap of In_xGa_（1-x）N alloy decreases considerably when the In constituent x increases. It is the interactions of s–s and p–p orbitals between anions and cations that play significant roles in formatting the band gaps bowing. In general, the HSE06 hybrid functional could provide a good alternative to the PBE functional in calculating the band gap bowing parameters.

Unusual Brain Trauma Injury

Unusual head trauma is rare with various mechanisms of occurrence. The injuries can be similar to those of road accidents but sometimes with significant complexities. The objective was to determine the frequency of this pathology in our practice, describe the different mechanisms and report the craniocerebral lesions caused by this type of trauma. Materials and Method: This was a descriptive study with retrospective collection spread over a period of 3 years. After selecting the files, the patients and/or their companions were contacted by telephone to inquire about them and then returned to the consultation for reassessment. Disease history and information were obtained from patients’ medical records. Result: The frequency of this pathology was 1.78% and his incidence was 0.4 cases per month. The average age of the patients was 13.47 years. All the victims were male. 41.17% of patients were in school. The mechanisms of trauma were the hoof blow 47.1%, the horn blow 29.4% and the stone blow 11.7% respectively. 23.5% of patients were confused and 11.7% children were in coma. One patient presented an anisocoria. The motor deficit was present in 5 cases. CT-scan made it possible to highlight a skull depressing fracture 58.8% and confirm a craniocerebral wound in 35.3%. The average time between patient admission to hospital and completion of surgery was 24.5 hours. The surgery had consisted of the trimming of cranio-cerebral wounds, exploration, duroplasty and lifting of skull depressing fracture. After 15 months of follow-up, the evolution was favorable in 53.3%, the morbidity was 33.4% and the mortality 17.6%. Conclusion: These are rare but serious conditions because they are fatal and disabling. An early and multidisciplinary management can hope to have a good favorable.

Surgical strategy of the treatment of atypical femoral fractures

The atypical femoral fracture(AFF)has been attracting significant attention because of its increasing incidence;additionally,its treatment is challenging from biological and mechanical aspects.Although surgery is often required to manage complete AFFs,clear guidelines for the surgical treatment of AFFs are currently sparse.We reviewed and described the surgical treatment of AFFs and the surveillance of the contralateral femur.For complete AFFs,cephalomedullary intramedullary nailing spanning the entire length of the femur can be used.Various surgical techniques to overcome the femoral bowing common in AFFs include a lateral entry point,external rotation of the nail,and the use of a nail with a small radius of curvature,or a contralateral nail.In the case of a narrow medullary canal,severe femoral bowing,or pre-existing implants,plate fixation may be considered as an alternative.For incomplete AFFs,prophylactic fixation depends on several risk factors,such as a subtrochanteric location,presence of a radiolucent line,functional pain,and condition of the contralateral femur;the same surgical principles as those in complete AFFs can be applied.Finally,once AFF is diagnosed,clinicians should recognize the increased risk of contralateral AFFs,and close surveillance of the contralateral femur is recommended.

Experimental and numerical analysis on suitability of S-Glass-Carbon fiber reinforced polymer composites for submarine hull

Suitability of S-Glass/carbon fiber reinforced polymer composite for submarine hull subjected to hydrostatic pressure has been investigated in the present study.Metallic materials have raised concerns owing to their decomposition due to low resistance towards salinity and hence polymer composites have been explored to showcase their mechanical stability to withstand transverse and impact loads.To this end,the mechanical properties of S-Glass/carbon fiber reinforced polymer composite were experimentally investigated and higher specific strength and stiffness of the composite in comparison to many metallic materials used for submarine hull were reported.The obtained experimental values were used for the static and dynamic crash analysis of the bow,stern and foil through Finite Element Analysis(FEA);where depth of travel was varied from sea surface level of 0-7000 m.Submarine assembly was later developed with the optimum shape and thickness of each part.We also report the nonlinear crash analysis upon impact at velocity ranging from 3 to 21 m/s.Besides,kinetic energy,acceleration peak and internal energy in struck submarine revealed that travel depth 1750 m and 3500 m is recommendable,more particularly,crash safety factor of the submarine is found to be within limit when submarine encounters crash at 1750 m.

The Mars orbiter magnetometer of Tianwen-1:in-flight performance and first science results

The Mars Orbiter MAGnetometer(MOMAG)is a scientific instrument onboard the orbiter of China’s first mission for Mars—Tianwen-1.Since November 13,2021,it has been recording magnetic field data from the solar wind to the magnetic pile-up region surrounding Mars.Here we present its in-flight performance and first science results,based on its first one and one-half months’data.Comparing these early MOMAG observations to the magnetic field data in the solar wind from NASA’s Mars Atmosphere and Volatile EvolutioN(MAVEN)mission,we report that the MOMAG magnetic field data are at the same level in magnitude,and describe the same magnetic structures with similar variations in three components.We recognize 158 clear bow shock(BS)crossings in these MOMAG data;their locations match well statistically with the modeled average BS.We also identify and compare five pairs of datasets collected when Tianwen-1’s orbiter and the MAVEN probe made simultaneous BS crossings.These BS crossings confirm the global shape of modeled BS,as well as the south-north asymmetry of the Martian BS.Two cases presented in this paper suggest that the BS is probably more dynamic at flank than near the nose.So far,MOMAG performs well,and provides accurate magnetic field vectors.MOMAG is continuously scanning the magnetic field surrounding Mars.Data from MOMAG’s measurements complement data from MAVEN and will undoubt edly advance our understanding of the plasma environment of Mars.

一种新型多用途污染控制船的研发及其球鼻艏的优化

Controlling marine pollution caused by hydrocarbons spilling from oil tanker accidents and oil rigs is urgently needed.Conventional pollution control vessels currently in service worldwide do not meet certain safety criteria,storage capacities,and response times owing to their technical shortcomings.This study proposes a new concept of multimission and autonomous antipollution vessels capable of acting quickly and efficiently to counter such pollution threats.The objective of this study is to carry out a total and rapid recovery of the spilled oil slick in complete safety.Hence,optimizing the bulbous bow adapted to the pollution control vessel during its displacement is necessary to horizontally straighten the accompanying waves formed around the hull and to laminate the flow upstream of the side openings for the recovery of spilled oil.This optimization improves the nautical qualities specific to this ship to reduce the total resistance to progress and to standardize the flow upstream of the side openings to allow the collection of spilled oil at high speed.This optimization study can open a field of application for the construction of modern multi-mission pollution control vessels.Tests in hull basins will be planned to validate and adjust the results obtained from the simulations.

ICP刻蚀硅形貌控制研究

硅的刻蚀形貌控制是MEMS器件加工中的关键技术之一,形貌控制是硅表面刻蚀和钝化反应取得平衡的结果,任何影响刻蚀和钝化反应的因素都会影响到刻蚀形貌。采用中科院微电子研发中心研制的基于化学平衡原理的ICP-98A等离子刻蚀机,对ICP刻蚀当中影响形貌的关键工艺参数进行了研究和分析,研究了源功率RF1、射频功率RF2及气体(SF6和C4F8)比例对刻蚀形貌的影响,分析了bow ing现象产生机制,并给出了降低这种现象的工艺方法。该研究对提高硅的ICP刻蚀形貌控制具有重要的指导意义。

Atypical case of bow hunter’s syndrome linked to aberrantly coursing vertebral artery: A case report

BACKGROUND In bow hunter’s syndrome(BHS),also known as rotational vertebral artery(VA)syndrome,there is dynamic/rotational compression of the VA producing verte-brobasilar insufficiency.Most occurrences involve atlantoaxial rather than mid-cervical VA compromise,the latter being rarely reported.Herein,we detail successful VA decompression at mid-cervical spine,given a departure from its usual course.CASE SUMMARY The patient,a 45-year-old man,presented to our hospital with occipital headache and vertigo.Computed tomography angiography showed anomalous C4 entry of right VA,with compression upon head rotation to that side.Thyroid cartilage and anterior tubercle of C5 transverse process were visibly at fault.We opted for sur-gery,using an anterior cervical approach to remove the anterior tubercle.Patient recovery was uneventful and brought resolution of all preoperative symptoms.CONCLUSION BHS is an important consideration where aberrant coursing of VA and neurologic symptoms coexist.

Deep Learning-Based Digital Image Forgery Detection Using Transfer Learning

Deep learning is considered one of the most efficient and reliable methods through which the legitimacy of a digital image can be verified.In the current cyber world where deepfakes have shaken the global community,confirming the legitimacy of a digital image is of great importance.With the advancements made in deep learning techniques,now we can efficiently train and develop state-of-the-art digital image forensic models.The most traditional and widely used method by researchers is convolution neural networks(CNN)for verification of image authenticity but it consumes a considerable number of resources and requires a large dataset for training.Therefore,in this study,a transfer learning based deep learning technique for image forgery detection is proposed.The proposed methodology consists of three modules namely;preprocessing module,convolutional module,and the classification module.By using our proposed technique,the training time is drastically reduced by utilizing the pre-trained weights.The performance of the proposed technique is evaluated by using benchmark datasets,i.e.,BOW and BOSSBase that detect five forensic types which include JPEG compression,contrast enhancement(CE),median filtering(MF),additive Gaussian noise,and resampling.We evaluated the performance of our proposed technique by conducting various experiments and case scenarios and achieved an accuracy of 99.92%.The results show the superiority of the proposed system.

基于模糊Bow-tie模型的城镇燃气管道泄漏定量风险评价

燃气管道事故一旦发生后果大多比较严重。为全面分析燃气管道风险的前因后果,确定重点维护和监控的管段区域,引入了Bow-tie模型,将管道泄漏的故障树与事件树统一到一起对燃气管道进行定量风险评价。采用模糊集相关理论与专家评价相结合的方法得出管道泄漏的模糊可能值;然后基于模糊层次分析法确定管道泄漏后果因素的权重系数;再通过矩阵乘法求得泄漏后果值。以某段燃气管线为案例,全面识别出各风险因素,量化得到管道各泄漏后果事件的风险值。实际应用结果表明:①该方法可快速合理地评判出管道系统的相对风险大小;②三角模糊数与层次分析法的应用减少了传统评价中主观及模糊因素产生的评价偏差,使得评价结果更接近客观实际;③依据评价结果制订有针对性的预防维护措施,能够实现有限维护资源的合理配置,保障燃气管道的安全可靠运行。

Flow Field Improvement by Bowed Stator Stages in a Compressor with Different Axial Gaps Under Near Stall Condition

The outlet flow fields of a low-speed repeating-stage compressor with bowed stator stages are measured with five-hole probe under the near stall condition when the rotor/stator axial gap varies. The performances of the straight stator stages are investigated and compared to those of the bowed stator stages. The results show that using bowed stator stages could alleviate the flow separation at both upper and low corners of the suction surface and the endwalls, and decrease the losses along the flow passage as well as the outlet flow angle. As the rotor/stator axial gap decreases, although the diffusion capacity of the compressor increases obviously, the outlet flow field in the straight stator stages deteriorates quickly. By contrast, little changes occur in the bowed stator stages, indicating that as the rotor/stator axial gap decreases, improved performance is achieved in the bowed stator stages.

特征点显著性约束的图像检索方法

图像检索的Bag of Words体系存在量化后的视觉词影响局部特征的辨别能力并且缺乏特征之间空间关系的缺点,影响检索效率。针对复杂背景的目标查询,提出了融合显著性信息的图像检索方法和基于显著特征点空间距离比的后验证方法。首先,提取图像显著目标区域,使用空间金字塔模型进行图像检索。然后,利用查询图像与检索图像匹配的显著特征对,计算任意两对显著特征点的距离比,保留满足阈值的比值,并求和,用以重新排序结果图像,得到最终的检索结果。实验结果表明:该方法显著提高了检索的精确度,并减少了几何验证过程的运算时间。

基于改进稀疏编码模型的图像分类算法

针对图像表示,提出了一种基于改进稀疏编码模型的图像分类算法.首先,提取表示图像视觉局部特征的SIFT(Scale-Invariant Feature Transform)描述子;然后,利用稀疏编码方法生成基于SIFT描述子的视觉词汇库,将SIFT描述子编成稀疏向量;通过有效稀疏向量的区域融合和空间结合而获取整体的稀疏向量并用于图像表示;最后,采用随机森林多分类器对稀疏向量进行训练和测试.结果表明,与现有的算法相比,该算法的性能更佳,可以有效表示图像的特性并提高其分类的准确率.