Maximum Ratio Combining Precoding for Multi-Antenna Relay Systems

This paper addresses the design of practical communication strategies for multi-antenna amplify-and-forward and decode-and-forward relay systems. We show that simple linear techniques at the source and destination in conjunction with maximum ratio combining can provide an optimal transmission strategy in terms of received SNR without imposing a huge computational load over the relay node(s). Besides, the structures of precoding matrices are very similar at the source and relay nodes, which reduces the complexity as all nodes can play the role of source and relay nodes without changing their transmission structure. Numerical results show that the proposed transmission and reception techniques can improve the received SNR, and hence enhance the ergodic capacity.

A Cooperative Diversity Analysis of Two User Mobile Communication System with Maximal Ratio Combining

Cooperative communication is going to play a vital role in the next generation wireless networks. In this paper we derive the expression for symbol error probability (SEP) of a two-user cooperative diversity system, where two users cooperate through the decode-and-forward (DF) relaying with binary phase-shift keying (BPSK) modulation in a flat Rayleigh fading environment. We compare the computational results obtained by the SEP expression with the simulation results using maximal-ratio combining (MRC), equal-gain combining (EGC) and selection combining (SC) techniques. Numerical results show the performance of a cooperative diversity system with maximal-ratio combining is giving better results compared to SC and EGC techniques.

EFFICIENT BIT ERROR PROBABILITY EXPRESSION AND VERY TIGHT BOUND FOR MAXIMAL RATIO COMBINING DIVERSITY SYSTEMS OVER RAYLEIGH FADING CHANNEL

Bit Error Probability (BEP) provides a fundamental performance measure for wireless diversity systems. This paper presents two new exact BEP expressions for Maximal Ratio Combining (MRC) diversity systems. One BEP expression takes a closed form, while the other is derived by treating the squared-sum of Rayleigh random variables as an Erlang variable. Due to the fact that the extant bounds are loose and could not properly characterize the error performance of MRC diversity systems, this paper presents a very tight bound. The numerical analysis shows that the new derived BEP expressions coincide with the extant expressions, and that the new approximation tightly bounds the accurate BEP.

Calibration of LRFD Format for Steel Jacket OffshorePlatform in China Offshore Area(2): Load, Resistance and Load Combination Factors

Adopting the load and resistance factor design format, the design method for steel jaeket platform structures is developed. Firstly, the limit state equations and design format for steel jacket platform structures are introduced. Then, the ratio of live load effect to dead load effect is estimated. The target reliabilities for design of offshore structures in China offshore area are calibrated by past practice in API RP2A-WSD code. The load and resistance factors are optimized by minimizing the difference within the target reliability and the resulting reliability over the range of load effect ratios. Considering the concurrence of different loads, load combination factors are obtained through an optimization process, and the relation between the load combination factor and load correlation coefficient is established. Finally, the design formulae for steel jacket structures in China offshore area are recommended.

Glycated haemoglobin reduction and fixed ratio combinations of analogue basal insulin and glucagon-like peptide-1 receptor agonists:A systematic review

BACKGROUND Fixed ratio combinations(FRCs)of analogue basal insulin and glucagon-like peptide-1 receptor agonists are a newer addition to the therapeutic armamentarium for the management of type 2 diabetes mellitus.They reduce treatment complexity by combining two injectables in a single daily injectable,thus potentially improving adherence and persistence.Clinicians wanting to use FRCs would need to choose between members of the class.AIM To describe and contrast the glycated haemoglobin reduction of two FRCs of analogue basal insulin and glucagon like peptide-1 receptor agonist in adults with type 2 diabetes mellitus.METHODS The following Population,Intervention,Comparison,Outcome question was used for the primary analysis:Among adult patients with type 2 diabetes mellitus[P],what is the effect of iGlarLixi[I]compared to IDegLira[C]for bringing about glycaemic control(as measured by reduction in glycosylated haemoglobin)[O]?The Prisma Statement was used as a guideline for framing this systematic review.We searched PubMed,EMBASE and Cochrane library databases and Clinicaltrials.gov using various keywords and medical search headings related to type 2 diabetes mellitus,iGlarlixi,IDegLira and glycated haemoglobin A1c.RESULTS All 14 studies identified by the systematic search met the primary efficacy endpoint of reduction in glycated haemoglobin.There were no head-to-head studies between the FRCs of iGlarlixi and IDegLira,and we therefore did an indirect comparison based on a common comparator of insulin glargine U100.Both iGlarLixi and IDegLira effectively reduce glycated haemoglobin when compared to insulin glargine U100.However,using indirect comparisons,IDegLira had a greater haemoglobin A1c reducing ability(0.6%vs 0.3%).The indirect comparison is limited by the differences between the studies;the fasting blood glucose targets were slightly higher for iGlarLixi studies when compared to the IDegLira studies(4.0-5.0 mmol/L and 4.4-5.6 mmol/L),and the IDegLira study used a greater average dose of insulin glargine when compared to the iGlarLixi studies(66 U/d vs 40 U/d).CONCLUSION Both iGlarLixi and IDegLira effectively reduce glycated haemoglobin.Indirect comparisons,using insulin glargine as the common comparator,suggest that IDegLira reduces glycated haemoglobin to a greater extent than iGlarLixi.However,given the limitations of indirect comparisons,robust head to head studies and real-world data would better inform clinician choice and clinical practice guidelines.

UPLINK PERFORMANCE OF CWP-MC-CDMA WITH SPACE DIVERSITY COMBINING TECHNIQUE OVER RAYLEIGH FADING CHANNEL

In this paper, a Complex Wavelet Packet based Multi-Carrier Code Division Multiple Access (CWP-MC-CDMA) system uplink model is proposed, based on the analysis of the principle of MC-CDMA and the use of the optimized complex wavelet packet. Considering that the base station can adopt multiple re-ceiver antennas in the uplink, we employ the Space Diversity Combining (SDC) technique to improve the sys-tem performance via multiple antennas. The uplink performance of proposed CWP-MC-CDMA system with SDC technique is investigated over Rayleigh fading channel, and corresponding bit error rate analysis is given in detail. The system can avoid the decrease of spectrum efficiency of conventional MC-CDMA due to insert-ing cyclic prefix. Theoretical analysis and simulation result show that the application of SDC technique can improve the CWP-MC-CDMA system ability to combat spatial fading and various interferences effectively. Moreover, the proposed system based on SDC technique has superior Bit Error Rate (BER) performance over the Discrete Fourier Transform (DFT) and SDC based MC-CDMA system and the real wavelet packet and SDC based MC-CDMA system.

An Evaluation of Genotoxicity and Cytotoxicity of Melamine in Combination with Cyanuric Acid at Three Mass Ratios

Melamine in combination with cyanuric acid has been considered to be more toxic than either melamine or cyanuric acid alone. The objective of this study was designed to evaluate the combined genotoxicity and cytotoxicity of melamine （M） and cyanuric acid （C） at three mass ratios （1：1, 1：2, 2：1）. MC （1：1）, MC （1：2）, and MC （2：1） were evaluated for their potential genotoxic risk, at gene level by Ames test, and at chromosomal level by micronucleus test. In order to evaluate cytotoxicity in HEK-293 cells, the MTT assay was included. Western blot was also employed to investigate the renal injury molecule-1 （Kim-1） expression in HEK-293 cells exposed to MC. Neither genotoxicity at gene level nor at chromosomal level was observed for MC （1：1）, MC （1：2）, and MC （2：1）. Based on MTT assay, three ratios of MC at 82.5 and 165 μg/mL slightly inhibited viability of HEK-293 cells （P〈0.05）. MC （1：1） at 41.25 and 82.50 IJg/mL could elevate the Kim-1 expression in HEK-293 cells.

Diagnostic Method and Adaptability Analysis of Multiple Water Breakthroughs in Horizontal Well in Combined Well Pattern

The combined well pattern has been widely used in reservoir development, with a common pattern being a horizontal well in the center for oil production and multiple vertical wells around for water injection. For this type of well pattern, determining the horizontal well is affected by which injection wells, especially when the injecting water breaks through, accurately determining the direction of water inflow will provide an important basis for targeted water well measures. Based on the production performance data of horizontal wells, the semi logarithmic relationship curves of water-oil ratio, derivative water-oil ratio, and cumulative production were used for the first time to determine the breakthrough problem of water injection in the surrounding water injection wells of horizontal wells based on their response characteristics. The adaptability of this method under different influencing factors was analyzed. Introducing the parameter of cumulative production not only preserves the variation trend of the derivative of water-oil ratio with time, but also facilitates the processing of actual production data.

Design Technology of Continuous Beam-Arch Combination Bridges

In this paper,a research was conducted on the design technology of continuous beam-arch composite bridges.A brief introduction is given on the of continuous beam-arch composite bridges,its basic mechanical characteristics is analyzed,and three aspects of design technology is studied,which are rise-span ratio,stiffness ratio,and bridge deck cracking.This article acts as a reference for relevant design units in China to improve the design of continuous beam-arch combination bridges.

融合多源数据挖掘信息的非轴对称端壁/叶身联合成型设计空间知识挖掘

为厘清联合成型设计空间各造型方法对涡轮叶栅性能提升的贡献,将基于总变差分析的全局敏感性分析方法与平行坐标系及直方图、散点图等可视化技术相结合,提出了将多源数据挖掘信息进行融合的设计空间知识挖掘框架,并利用该框架对某小展弦比叶栅端壁/叶身联合成型设计空间进行知识挖掘。结果表明:叶栅气动损失增减对基元型线微调十分敏感;非轴对称端壁所带来的损失减少量与型线微调接近,但设计空间内不同非轴对称端壁样本性能波动较小,导致其重要性被全局敏感性分析方法低估;虽然单独采用弯叶片难以整体降低小展弦比叶栅损失,但将弯、型线微调和非轴对称端壁造型相结合可获得“1+1+1>3”的性能增益;在端壁/叶身联合成型设计空间内,将基元型线朝着后加载方向微调,并采用喉部附近下凹较深的非轴对称端壁造型及反弯叶片设计,可获得气动损失较小的叶栅设计。研究结果明晰了端壁/叶身联合成型设计空间优化解特征,可为类似小展弦比叶栅设计优化提供借鉴。

摩擦阻尼器组合支座的隔震优化对比

为解决一种摩擦阻尼器组合隔震支座的有效性及计算方法的问题,研究了用于结构设计有限元建模的组合元件计算模型,包括水平向、竖向刚度和滞回模型。使用有限元软件SAP2000,对比研究了布置有该组合支座的优化隔震方案和传统橡胶支座的隔震优化方案在高宽比不同的高层框架剪力墙筒体结构的抗震性能。结果表明:与传统隔震支座方案相比,组合隔震支座隔震方案可适当延长结构自振周期,减小隔震层侧移,有效降低支座拉应力,提高支座的抗倾覆能力和支座耗能,还可有效降低上部结构的层间剪力及侧移等地震响应,证明组合隔震支座方案较传统隔震支座方案综合性收效明显。

预制UHPC永久模板钢筋混凝土组合梁抗剪性能有限元分析

为了研究预制超高性能混凝土永久模板钢筋混凝土组合梁抗剪性能,选取合适的U型UHPC预制单元本构关系,建立了钢筋混凝土梁的有限元永久模型,并与已有的试验数据进行比较,验证了模型的可靠性,并分析配箍率、剪跨比等参数对超高性能混凝土组合梁抗剪性能的影响。结果显示:超高性能混凝土预制单元可显著提高斜向开裂荷载和极限荷载;预制单元会限制箍筋的作用,所以配箍率对组合梁影响小;剪跨比对组合梁抗剪性能影响大,但是和配箍率一样都会影响其延性。

施肥对云南松苗木-土壤氮、磷、钾化学计量比的影响

【目的】了解外源氮、磷添加后云南松苗木各器官及土壤中氮、磷、钾化学计量比的变化特征,为云南松苗木培育过程中养分的合理管理提供依据。【方法】以2年生云南松苗木为试材,设置氮、磷配施试验,每种肥料设置3个施肥水平,氮肥的施用水平为0,0.4和0.8 g/株,磷肥的施用水平为0,0.8和1.6 g/株,共9个施肥处理组合。施肥后2,4,6个月分别测定苗木根、茎、叶及土壤的氮(N)、磷(P)、钾(K)含量,计算N∶P、N∶K、K∶P,探讨施肥对云南松苗木-土壤氮、磷、钾化学计量比的影响。【结果】施肥处理后2,4,6个月,9个施肥处理组合的云南松苗木根、茎、叶平均N∶P分别为2.85~4.30,3.60~5.12和5.18~6.65,总体上表现为氮受限,其中根的平均N∶P以氮肥0.8 g/株+磷肥0.8 g/株处理最小,茎、叶的平均N∶P以氮肥0.4 g/株+磷肥0.8 g/株处理最小;平均K∶P分别为3.72~5.87,5.04~7.26和5.62~7.71,均以氮肥0.4 g/株+磷肥0.8 g/株处理最小;平均N∶K分别为0.71~0.78,0.71~0.74和0.89~0.93,总体上均以氮肥0.4 g/株处理最大。根、叶N∶P、K∶P随苗木的生长呈现降低趋势,茎N∶P、K∶P表现为先降低后升高的趋势;根、叶N∶K随苗木的生长呈现出先降低后增加的趋势,茎N∶K呈现增加趋势。施肥后2,4,6个月各施肥处理组合土壤的平均N∶P、N∶K和K∶P分别在3.48~4.58,0.70~0.74,4.93~6.52内波动,随着时间推移,N∶P、K∶P呈现先降低后增加的趋势,N∶K呈增加趋势。氮、磷配施改变了苗木与土壤的相关关系,且这种关系存在明显的时间变异,施肥处理后2个月内云南松苗木各器官与土壤化学计量间无明显的相关关系,而随时间延长,呈显著相关关系。【结论】综合来看,氮、磷配施改变了苗木及土壤的氮、磷、钾化学计量比,表现为降低了苗木及土壤的N∶P、K∶P,提高了苗木及土壤的N∶K。随着时间变化,N∶P、K∶P总体上呈现出降低的趋势,N∶K呈现出逐渐增加的趋势,表明氮限制有加剧趋势。

咸淡水组合灌溉对土壤盐分和棉花生长的影响

为揭示不同微咸水(农田排水)与淡水在“先咸后淡”的组合灌溉模式下对土壤容重、盐分迁移和棉花生长的影响。以淡水灌溉为对照(CK),设置7种不同微咸水、淡水组合灌溉(微咸水∶淡水=1∶14(T1)、2∶13(T2)、3∶12(T3)、6∶9(T4)、9∶6(T5)、12∶3(T6)),T7处理采用全额微咸水灌溉,于2022年4-9月进行了棉花田间试验。结果表明,采用微咸水灌溉造成土壤表层盐分积累,0~40 cm土层出现积盐现象,棉花生育期结束后,各处理与淡水对照(CK)比较,T1~T6在0~40 cm土层的电导率分别增加1.16%~26.61%,T7处理电导率增加86.40%;与淡水对照相比,组合灌溉后各处理土层0~40 cm土壤容重明显增加,土壤孔隙度降低,以全额微咸水灌溉T7处理最为显著(容重增加10.24%);微咸水组合灌溉有效提高棉花株高、叶面积指数、茎粗。合理利用微咸水组合灌溉能够为棉花生长提供良好的水盐环境,提高棉花产量,能够为极端干旱区合理利用微咸水提供一种新的灌水模式,为灌区发展节水灌溉及农业可持续发展提供理论支撑。

三维多回波聚合梯度回波序列在腰骶丛成像中的初步应用

目的 探讨3D多回波聚合梯度回波序列(3D GEMEC)在腰骶丛神经成像中的应用价值。方法 回顾性分析2022年8~9月六安市人民医院以腰腿疼为主诉的32例住院患者的影像学资料,男15例,女17例,年龄28~78(60.1±15.8)岁。在不同1.5T平台上分别完成腰骶丛3D GEMEC序列和三维T2加权快速梯度回波(3D T2 FFE)序列,比较两种序列腰骶丛神经的信噪比、对比噪声比和主观显示效果。结果 3D GEMEC序列腰骶丛神经的信噪比、对比噪声比以及主观显示效果与3D T2 FFE序列的差异均无统计学意义(P=0.250、0.146、0.083)。结论 3D GEMEC序列可以清晰地显示腰骶丛神经的解剖结构并抑制背景信号,在腰骶丛神经病变的诊断方面具有一定的临床应用前景。

基于QAM的协作通信系统物理层认证技术

针对两用户协作通信系统的身份认证问题,提出了一种基于正交幅度调制(QAM)的协作物理层认证机制。在该机制中,两个单天线用户分别使用同相与正交分量传输自己及伙伴的消息和标签,从而实现两用户消息和标签的唯一分解。基站采用最大比合并检测用户消息和标签,并通过标签对比完成物理层身份认证。在等功率分配且用户上行信道对称的典型场景下,给出了消息和标签的误码率闭合表达式。结果表明:在信噪比(SNR)为6~15 dB时,所提机制的认证概率与非协作物理层认证相比提高了12%~20%,非法攻击认证概率仅保持在10^(-3)量级,所提认证机制具有更好的身份认证性能。

铁蛋白/淋巴细胞比值在评估DM/PM-ILD严重程度中的诊断准确性研究

目的探讨铁蛋白/淋巴细胞比值对皮肌炎/多肌炎合并间质性肺病(DM/PM-ILD)预后不良的预测价值。方法回顾性收集2018年6月-2020年12月南昌大学第一附属医院风湿免疫科就诊具有完整临床资料的皮肌炎/多肌炎合并间质性肺病患者86例。根据HRCT和美国胸科学会和欧洲呼吸学会关于特发性肺纤维化的国际共识声明将患者分为缓解组(n=29)和加重组(n=57)。对两组的人口学特征,临床症状和实验室检查进行比较。通过计算患者ROC曲线,确定FLPR对DM/PM-ILD严重程度的诊断能力。结果加重组患者ESR、CRP、SF、LDH、LLR、SII和FLPR显著高于缓解组患者(P<0.001)。多因素Logisitic回归分析得出,SF、LDH、低淋巴细胞、LLR、SII和FLPR是加重组DM/PM-ILD患者的独立危险因素。ROC曲线分析得出,FLPR曲线下面积为0.947,敏感度为0.649,特异度为1,界值为599。结论铁蛋白/淋巴细胞比值是评估DM/PM-ILD患者严重程度的有效生物标志物,为DM/PM合并ILD患者提供了最佳的临界值,从而使诊断效率最大化。

基于阻抗法的光储逆变器交直流建模及耦合分析

在共母线式光储逆变器中,交直流单元通过直流母线电容连接。传统的逆变器建模方法将母线电容视为无穷大,认为交直流侧运行相互解耦。然而,当直流母线电容较小时,光储逆变器的交直流侧将产生交互影响,引起电流谐振。该文以单个单元稳定运行为前提,推导出直流共母线系统稳定性的合阻抗比(CIR)判据。该判据的数学形式便于利用Bode图对并联系统的谐振源进行分析与定位。首先,对光储逆变器交直流各单元进行阻抗建模,利用合阻抗比判据分析直流侧储能单元相对于光伏单元更易与网侧发生谐振。然后,通过在电流环路加入陷波器改善储能单元的阻抗特性。最后,仿真及实验结果证实了所提合阻抗比稳定性判据的正确性。

NLPR、hsCRP/PA、PCT联合检测对重症急性胰腺炎的预测价值

目的 探讨中性粒细胞与淋巴细胞和血小板比值(NLPR)、超敏C反应蛋白(hsCRP)/前白蛋白(PA)、降钙素原(PCT)与重症急性胰腺炎(SAP)的相关性,并分析上述3个指标单独及联合检测对SAP的预测价值。方法 选取2016年2月—2022年1月宜宾市第一人民医院收治的急性胰腺炎(AP)患者205例,按病情严重程度分为非SAP组(n=155)和SAP组(n=50)。比较两组一般临床特征及评分,进行单因素分析,应用二元Logistic回归对NLPR、hsCRP/PA、PCT进行分析,比较联合预测因子、BISAP及Ranson评分预测价值。结果 二元Logistic回归分析发现NLPR、hsCRP/PA、PCT均为预测SAP的独立影响因素;ROC曲线结果显示,NLPR曲线下面积为0.68,最佳阈值为4.73;PCT曲线下面积为0.93,最佳阈值为0.39;hsCRP/PA曲线下面积为0.82,最佳阈值为0.44;联合预测因子曲线下面积为0.94,最佳阈值为0.13;联合预测因子的灵敏度及阴性预测率高于Ranson评分及BISAP评分。结论 NLPR、hsCRP/PA、PCT各指标在一定程度上可反映AP严重程度,可被视为早期预测SAP的指标,其联合预测因子具有较好的临床应用价值。

基于正态分布的双差波速比方法研究——以山东长岛震群为例

对于震源位置相对集中的震群活动,首先应用双差波速比法对台站到时数据进行2次差分,该方法充分利用不同台站纵横波的到时数据,无需地震发震时刻及位置信息,且将计算波速比范围限定在震源区附近,消除了震源区到台站传播路径的影响;然后运用正态分布的组合去除误差分布的影响,得到关于去除误差分布后的纵横波到时二维正态分布,通过公式推导确定了二维正态分布的相关系数;最后,通过计算置信椭圆长轴斜率得到长岛震群整体波速比。研究结果表明,长岛震群整体波速比为1.7275,等地震数滑动(60个)计算得到的波速比区间为[1.4887,3.0541];2017、2018年长岛震群波速比变化与震群活动过程密切相关,同时反映了震源区介质流体饱和度、裂隙密度和状态变化。