Improvement of breakdown characteristics of an A1GaN/GaN HEMT with a U-type gate foot for millimeter-wave power application

In this study, the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor （HEMT） with a U-type gate foot. The U-gate AlGaN/GaN HEMT mainly features a gradually changed sidewall angle, which effectively mitigates the electric field in the channel, thus obtaining enhanced off-state breakdown characteristics. At the same time, only a small additional gate capacitance and decreased gate resistance ensure excellent RF characteristics for the U-gate device. U-gate AlGaN/GaN HEMTs are feasible through adjusting the etching conditions of an inductively coupled plasma system, without introducing any extra process steps. The simulation results are confirmed by experimental measurements. These features indicate that U-gate A1GaN/GaN HEMTs might be promising candidates for use in millimeter-wave power applications.

Dynamic Response of the U-Typed Sandwich Panel Under Explosion Load Based on the SDOF Method

Sandwich panel is commonly used in ship and marine engineering equipment,such as side structure and superstructure deck of a ship,which is of good anti-explosion performance.This paper addresses a study on the dynamic response of the U-typed sandwich panel under explosion load through the numerical simulation and theoretical methods.Based on the orthotropic plate theory,the U-typed sandwich panel is simplified and transformed into a single degree of freedom(SDOF)spring system,the equivalent motion equation of the SDOF system and the expression of triangular explosion load function are established based on the SDOF theory,and the maximum response spectrum of the SDOF system is obtained.Then,the response of the equivalent SDOF system of the U-typed sandwich panel under explosion load is analyzed,and the theoretical results match well with the numerical simulation results,which verifies the accuracy of the theoretical method proposed in this paper.The theoretical method proposed in this paper could have good engineering applications for the structural anti-explosion design,and provide a reference for the evaluation of the anti-explosion performance of ship and offshore platform structures.

U-Type Designs via New Generalized Partially Balanced Incomplete Block Designs with <i>m</i>= 4, 5 and 7 Associated Classes

The traditional combinatorial designs can be used as basic designs for constructing designs of computer experiments which have been used successfully till now in various domains such as engineering, pharmaceutical industry, etc. In this paper, a new series of generalized partially balanced incomplete blocks PBIB designs with m associated classes (m = 4, 5 and 7) based on new generalized association schemes with number of treatments v arranged in w arrays of n rows and l columns (w ≥ 2, n ≥ 2, l ≥ 2) is defined. Some construction methods of these new PBIB are given and their parameters are specified using the Combinatory Method (s). For n or l even and s divisor of n or l, the obtained PBIB designs are resolvable PBIB designs. So the Fang RBIBD method is applied to obtain a series of particular U-type designs U (wnl;) (r is the repetition number of each treatment in our resolvable PBIB design).

Mitigation of long-term heat extraction attenuation of U-type medium-deep borehole heat exchanger by climate change

U-type medium-deep borehole heat exchanger(U-MDBHE)is a sustainable building heating technology.Current studies assess the long-term thermal performance of U-MDBHE using typical meteorological year weather data.The conclusions indicate a discernible deterioration in the thermal performance of U-MDBHE attributed to heat extraction attenuation.The thermal performance deterioration leads to the oversize of U-MDBHE and hinders the widespread application of U-MDBHE.This study introduces a novel idea that the long-term thermal performance of U-MDBHE should be evaluated considering climate change(CC)and verifies that the favorable effects of CC on the thermal performance of U-MDBHE can effectively mitigate the adverse effect of heat extraction attenuation.The favorable effects of CC include reducing the heating demand(due to the reduced building heating load(BHL)caused by CC)and improving the heating supply capacity(due to the enhanced outlet temperature caused by CC).In addition,the reduced BHL under CC enhances the inlet temperature of U-MDBHE,thereby improving its operation safety.CC mitigates the heat extraction attenuation of U-MDBHE,with the strongest effect in the ascending well,followed by the descending well,and then the butted well.Case studies using experimentally validated simulations on the 30-year operation of U-MDBHE demonstrate that by mitigating the adverse effect of the heat extraction attenuation,CC reduces the accumulated energy consumption by 14.31%–26.59%and improves the operation safety by up to 100%in Harbin(severe cold region)and Beijing(cold region).This study significantly contributes to improving the long-term thermal performance of U-MDBHE.

板坯落料方向对类U型件拉深成形质量的影响

分析了轿车左右后纵梁拉深成形特点及板料的面内各向异性特征 ,应用 Barlat平面各向异性屈服准则 ,在不改变模具几何形状、压机参数和板料的机械性能的条件下 ,分析落料方向不同对其成形质量的影响 ,提出板料抗厚向变形能力小的方向与类 U型件开口方向一致时 ,不增加成本可以提高冲压件的成形质量。

多点弯曲成形的曲面U型件弯曲模结构

针对曲面U型件在弯曲过程中表面刮痕、塑性压痕、曲面侧壁皱曲问题,设计了一种在板料流入凹模过程中用滚动摩擦代替滑动摩擦和凹模尺寸可以调节的结构。通过多滚轮的点接触成形来逼近曲边形状,达到了提高弯曲件表面质量,增加结构柔性和实现曲面U型件弯曲的目的,并给出了具体的模具结构和设计要点。

U形单侧凹弯曲件模具设计

用转轴式弯曲模 ,可成形带侧凹的U形复杂弯曲件。对此 ,导出了成形干涉条件 ,给出了确定模具转轴中心可行区域的方法 ,可为此类弯曲模结构参数的设计提供依据。

U形管换热器尾部支撑结构的应用

针对U形管换热器尾部无支撑跨距大于GB 151规定的最大无支撑跨距时,U形管尾部如何支撑问题,介绍了石化装置建设工程中常用的2种结构形式,并对不同结构形式的制作过程进行了介绍,对其优缺点进行了比较。

落料、弯曲复合模设计

通过对U型弯曲件的工艺分析,合理设计了落料、弯曲复合模,即在一个工位完成切舌、弯曲、切断3个不同工序的复合模结构。介绍了该模具的工作过程及设计要点。经实际生产验证,产品质量、生产效率和经济效益均得到了不同程度的提高。在考虑模具结构及成本的前提下,提高了复合模及连续模在模具生产中的占有比例,符合模具设计的发展方向。

相山矿田南部浯漳花岗斑岩体年代学、地球化学及地质意义

相山矿田的铀矿床集中分布于相山北部和西部两个铀成矿带,其中北部花岗斑岩型铀矿床占资源总量的36.55%。前人从年代学、地球化学、控矿因素与成矿模式等多方面对相山北部花岗斑岩做了不同程度的研究,但对于南部具有相同地质特征的花岗斑岩研究较为薄弱。近年来在相山南部相继发现浯漳、刁元、上南等众多铀矿点且见有一百多米的矿化段,表明其具有较大找矿前景。本文选择相山南部浯漳花岗斑岩开展野外地质调查、地球化学特征和LA-ICP-MS锆石U-Pb定年等的系统研究,在厘定地质特征和成岩年代的基础上,探讨其岩石类型、构造环境及物质来源。研究结果如下:(1)花岗斑岩LA-ICP-MS锆石U-Pb定年结果显示,206Pb/238U年龄加权平均值分别为135.6±1.6Ma(MSWD=0.67,n=17)、135.2±1.5Ma(MSWD=0.95,n=19),集中在134~136Ma之间,属于早白垩世时期;(2)花岗斑岩Sr含量为154×10^-6~261×10^-6,Yb含量为2.65×10^-6~3.62×10^-6,具有低Sr高Yb特征,属浙闽型(S型)花岗岩;(3)花岗斑岩属于燕山晚期后造山伸展拉张构造环境的产物;(4)花岗斑岩来自中元古代上地壳部分熔融,未有明显地幔物质参与;(5)对比相山北部产铀花岗斑岩规模、岩相、年代学、地球化学等特征,浯漳花岗斑岩具有产铀可能性,相山南部地区至今找矿未有突破,可能是缺乏深部勘查工程,从而导致隐伏矿体未被发现。

一种大型U型件弯曲模具的设计和试验

高强度不锈钢的弯曲成型特性和低强度金属材料的弯曲成型特性不同,通过对一种大型U型工件的折弯成型模具的设计和试模以及模具的改进过程,阐述了这类材料弯曲成型模具设计的方法,并从中总结出了对于类似模具设计过程中应注意的事项。

NEW LOWER BOUNDS FOR LEE DISCREPANCY ON TWO AND THREE MIXED LEVELS FACTORIALS

The objective of this paper is to study the issue of uniformity on asymmetrical designs with two and three mixed levels in terms of Lee discrepancy. Based on the known formulation, we present a new lower bound of Lee discrepancy of fractional factorial designs with two and three mixed levels. Our new lower bound is sharper and more valid than other existing lower bounds in literature, which is a useful complement to the lower bound theory of discrepancies.

New Lower Bounds to Wrap-around L2-discrepancy for U-type Designs with Three-level

The objective of this paper is to study the issue of uniformity on three-level U-type designs in terms of the wrap-around L2-discrepancy.Based on the known formula,we present a new lower bound of wrap-around L2-discrepancy for three-level U-type designs and compare it with those existing ones through figures,numerical simulation and illustrative examples.

Robust U-type test for high dimensional regression coefficients using refitted cross-validation variance estimation

This paper aims to develop a new robust U-type test for high dimensional regression coefficients using the estimated U-statistic of order two and refitted cross-validation error variance estimation. It is proved that the limiting null distribution of the proposed new test is normal under two kinds of ordinary models.We further study the local power of the proposed test and compare with other competitive tests for high dimensional data. The idea of refitted cross-validation approach is utilized to reduce the bias of sample variance in the estimation of the test statistic. Our theoretical results indicate that the proposed test can have even more substantial power gain than the test by Zhong and Chen(2011) when testing a hypothesis with outlying observations and heavy tailed distributions. We assess the finite-sample performance of the proposed test by examining its size and power via Monte Carlo studies. We also illustrate the application of the proposed test by an empirical analysis of a real data example.

Establishment of magneto-dielectric effect and magneto-resistance in composite of PLT and Ba-based U-type hexaferrite

We are examining the behavior of a composite made of ferroelectrics with strong dielectric properties and ferrites with magnetic properties due to the rising need for materials for multipurpose devices.Many application avenues will be favored by the pairing of these materials’individual qualities with one another.Perovskite and U-type hexaferrite composite materials have been chosen for this study based on their magnetic and dielectric properties.The composites,(1−x)PLT−x(Ba1−3xNd2x)4Co2Fe36O60 where x=0.52,0.54,0.56,0.58 are prepared by solid state reaction method and phase formation was examined.Consideration has been given to the magnetic,dielectric,and magneto-dielectric properties.This work has established the link between the electric and magnetic domains while applying electric and magnetic forces to the materials.The magneto-dielectric research revealed magneto-electric coupling in all of the samples.However,the sample shows the maximum coupling for x=0.54 with MDR%values of 93.17%,which might be because this sample appears to have a high magneto-resistance(161%).

Assembly Unit Resource Balancing Strategy based on Discrete Production Mode

Aiming at the characteristics of obvious block division and strong discreteness in the assembly production mode of electronic products,this paper proposes a composite U-shaped flexible assembly line model,and establishes a multi-objective optimization mathematical model on this basis.According to the characteristics of the model,the improved ranked positional weight(RPW)method is used to adjust the generation process of the initial solution of the genetic algorithm,so that the genetic algorithm can be applied to the block task model.At the same time,the adaptive cross mutation factor is used on the premise that tasks between different blocks are not crossed during cross mutation,which effectively improves the probability of excellent individuals retaining.After that,the algorithm is used to iterate to obtain the optimal solution task assignment.Finally,the algorithm results are compared with actual production data,which verifies the validity and feasibility of the assembly line model for discrete production mode proposed in this paper.

地下室外墙后浇带立面挡板施工技术研究

围绕地下室后浇带施工技术进行深入探讨,构建一个全面的研究体系,涵盖后浇带的理论研究、工程实例分析、施工工艺流程、新旧工艺对比与质量控制措施。通过对比分析原始工艺与新工艺,揭示了新工艺在提高施工效率、保证结构安全和延长建筑物使用寿命方面的显著优势。采用实地考察、实验模拟和数据分析等方法确保研究结果的准确性和可靠性。主要发现包括新工艺在减少裂缝、提高混凝土整体性方面的显著效果,以及在质量控制方面的新策略和措施。核心结论指出,采用新工艺不仅能够有效解决传统后浇带施工中的诸多问题,还能提升整体工程质量,具有较高的应用价值和推广意义。

Some results on resolvable incomplete block designs

This paper is concerned with the uniformity of a certain kind of resolvable incomplete block (RIB for simplicity) design which is called the PRIB design here. A sufficient and necessary condition is obtained, under which a PRIB design is the most uniform in the sense of a discrete discrepancy measure, and the uniform PRIB design is shown to be connected. A construction method for such designs via a kind of U-type designs is proposed, and an existence result of these designs is given. This method sets up an important bridge between PRIB designs and U-type designs.

On the maximin distance properties of orthogonal designs via the rotation

Space-filling designs are widely used in computer experiments.They are frequently evaluated by the orthogonality and distance-related criteria.Rotating orthogonal arrays is an appealing approach to constructing orthogonal space-filling designs.An important issue that has been rarely addressed in the literature is the design selection for the initial orthogonal arrays.This paper studies the maximin L_(2)-distance properties of orthogonal designs generated by rotating two-level orthogonal arrays under three criteria.We provide theoretical justifications for the rotation method from a maximin distance perspective and further propose to select initial orthogonal arrays by the minimum G_(2)-aberration criterion.New infinite families of orthogonal or 3-orthogonal U-type designs,which also perform well under the maximin distance criterion,are obtained and tabulated.Examples are presented to show the effectiveness of the constructed designs for building statistical surrogate models.

Enhanced magneto-dielectric response in La-doped Co_(2)U hexaferrite

The U-type hexaferrites(Ba_(1−3x)La_(2x))4Co_(2)Fe_(36)O_(60)(x=0,0.05,0.10,0.15,0.20,0.25)have been synthesized by auto-combustion method.The work involves the study of structural,microstructural,dielectric,magnetic and magneto-dielectric properties of the prepared materials.The structural analysis has been done by X-ray diffraction technique along with Le Bail refinement which confirmed the pure hexagonal phase for all the samples.The microstructural analysis has been carried out by field-emission scanning electron microscopy.The vibrating sample magnetometer is used to measure the magnetic properties.The sample with a composition of x=0.15 has shown the maximum magnetization of approximately 73.31 emu/g with the remnant magnetization of 38.89 emu/g and coercive field of 1.77 kOe at room temperature.Moreover,the same sample has delivered the maximum mag-netodielectric response of about 54.18%at 1.5-T field.