Design of Ultra-Low Loss Highly Nonlinear Dispersion Flattened Octagonal Photonic Crystal Fibers

In this study, Octagonal Photonic Crystal Fiber (O-PCF) structures are designed for different air filling fractions with fixed pitch length of 2.2 μm. The light propagating characteristics of PCF structures such as effective refractive index, confinement loss, chromatic dispersion mode effective area and nonlinear coefficient are numerically analyzed. The simulation results show that the fibers have dispersion flattened, ultra-low loss highly nonlinear nature in the wavelength region 1.3 μm to 1.7 μm.

High birefringence, low loss, and flattened dispersion photonic crystal fiber for terahertz application

A type of photonic crystal fiber based on Kagome lattice cladding and slot air holes in a rectangular core is investigated. Full vector finite element method is used to evaluate the modal and propagation properties of the designed fiber.High birefringence of 0.089 and low effective material loss of 0.055 cm^-1 are obtained at 1 THz. The y-polarized fundamental mode of the designed fiber shows a flattened and near-zero dispersion of 0±0.45 ps · THz^-1· cm^-1 within a broad frequency range(0.5 THz–1.5 THz). Our results provide the theory basis for applications of the designed fiber in terahertz polarization maintaining systems.

GIS-based Effect Assessment of Soil Erosion Before and After Gully Land Consolidation: A Case Study of Wangjiagou Project Region, Loess Plateau

The Loess Plateau is one typical area of serious soil erosion in the world. China has implemented ′Grain for Green′(GFG) project to restore the eco-environment of the Loess Plateau since 1999. With the GFG project subsidy approaching the end, it is concerned that farmers of fewer subsidies may reclaim land again. Thus, ′Gully Land Consolidation Project′(GLCP) was initiated in 2010. The core of the GLCP was to create more land suitable for farming in gullies so as to reduce land reclamation on the slopes which are ecological vulnerable areas. This paper aims to assess the effect of the GLCP on soil erosion problems by studying Wangjiagou project region located in the central part of Anzi valley in the middle of the Loess Plateau, mainly using the revised universal soil loss equation(RUSLE) based on GIS. The findings show that the GLCP can help to reduce soil shipment by 9.87% and it creates more terraces and river-nearby land suitable for farming which account for 27.41% of the whole study area. Thus, it is feasible to implement the GLCP in places below gradient 15°, though the GLCP also intensifies soil erosion in certain places such as field ridge, village land, floodplain, natural grassland, and shrub land. In short, the GLCP develops new generation dam land and balances the short-term and long-term interests to ease the conflicts between economic development and environmental protection. Furthermore, the GLCP and the GFG could also be combined preferably. On the one hand, the GFG improves the ecological environment, which could offer certain safety to the GLCP, on the other hand, the GLCP creates more farmland favorable for farming in gullies instead of land reclamation on the slopes, which could indirectly protect the GFG project.

Strata consolidation subsidence induced by metro tunneling in saturated soft clay strata

To choose the optimum construction method of metro tunneling, we conducted research with numerical simulation on strata consolidation subsidence by dewatering, dynamic dewatering, and non-dewatering construction method, taking the integrated effects of fluid-solid coupling and tunneling mechanics into account. We obtained the curved surfaces of ground surface subsidence and strata consolidation subsidence. The results show that the quantity of ground surface subsidence is 31 mm for the non-dewatering method, 39 mm for the dynamic dewatering method, and 105 mm for the dewatering method. Their ratio is 1：1.3：3.4; and the percentages of strata consolidation subsidence to whole ground surface subsidence of each construction method is 27% （no-dewatering）, 50% （dynamic dewatering）, and 79% （dewatering）. It is obvious that the non-dewatering construction method is the most effective method to control the strata consolidation subsidence induced by metro tunneling in saturated soft clay strata, and it has been successfully applied to the construction of the Shenzben metro line 1.

Design and Numerical Analysis of Ultra-High Negative Dispersion, Highly Birefringent Nonlinear Single Mode Core-Tune Photonic Crystal Fiber (CT-PCF) over Communication Bands

This paper presents the development of a highly efficient CT-PCF (Core-Tune Photonic Crystal Fiber) with substantial birefringence, tailored for applications in high-bit-rate communication and sensing while minimizing signal loss. The design incorporates a modified broadband dispersion compensating structure, optimized for operation across the E, S, C, and L communication bands within a wavelength range spanning 1360 nm to 1625 nm. Notably, the CT-PCF demonstrates a remarkable birefringence of 2.372 × 10-2 at 1550 nm, surpassing traditional PCF structures. Single-mode performance is evaluated using the Higher Order Mode Extinction Ratio (HOMER) method, revealing a peak HOMER value of 104 at 1550 nm. Furthermore, at 1550 nm, the CT-PCF exhibits exceptional nonlinear characteristics, featuring a high nonlinearity of 50.74 W-1⋅Km-1 for y polarization. In comparison to existing designs, the proposed CT-PCF exhibits superior performance metrics and optical characteristics. Additionally, the y polarization dispersion coefficient of the CT-PCF at 1550 nm is measured at -3534 ps/(nm⋅km). Overall, the CT-PCF represents a significant advancement, outperforming established systems in terms of performance metrics and optical properties.

Study on concentration distribution and detonation characteristics for non-axisymmetric fuel dispersal

The study of non-axisymmetric fuel dispersal and detonation can provide reference for the prevention of industrial cloud explosion accidents and the design of fuel air explosive(FAE).The concentration and detonation fields of 85 kg cylindrical and fan-shaped fuel are investigated by experiments and numerical simulations.A dynamic model of the whole process for fuel dispersal and detonation is built.The concentration distribution of fuel is used as the initial condition to calculate the detonation stage,thus solving the initial value problem of detonation field.The phase and component changes of fuel cloud at different locations are compared.The fuel cloud is divided into directions of 0°,90°,135°and 180°.The results show that the maximum cloud radius is 20.94 m in 135°and the minimum is 12.04 m in 0°.The diameter of the detonation fireball is 53.6 m,and the peak temperature is 3455 K.The highest peak overpressure is 3.44 MPa in 0°and the lowest is 2.97 MPa in 135°.The proportion of liquid phase in 0°is22.90%,and the fuel loss is 11.8% and 9% higher than that in 135°and cylindrical charge,respectively.The stable propagation distance of blast wave in 135°is 42.50% longer than 0°and 28.37% longer than cylindrical charge.

Multi-Deployment of Dispersed Power Sources Using RBF Neural Network

Multi-deployment of dispersed power sources became an important need with the rapid increase of the Distributed generation (DG) technology and smart grid applications. This paper proposes a computational tool to assess the optimal DG size and deployment for more than one unit, taking the minimum losses and voltage profile as objective functions. A technique called radial basis function (RBF) neural network has been utilized for such target. The method is only depending on the training process;so it is simple in terms of algorithm and structure and it has fast computational speed and high accuracy;therefore it is flexible and reliable to be tested in different target scenarios. The proposed method is designed to find the best solution of multi- DG sizing and deployment in 33-bus IEEE distribution system and create the suitable topology of the system in the presence of DG. Some important results for DG deployment and discussion are involved to show the effectiveness of our proposed method.

一种低串扰近零超平坦色散七芯光子晶体光纤的设计

设计了一种七芯低串扰近零超平坦色散液体填充光子晶体光纤,利用有限元法模拟计算了色散、芯间串扰和弯曲损耗等性能.数值模拟结果表明,该多芯光纤在实现近零宽带超平坦色散的同时,显著抑制了芯间串扰和弯曲损耗.在波长为1.38~1.74μm时,色散值介于0±0.5 ps/(km·nm)之间,且色散斜率介于0±0.02 ps/(km·nm^(2))之间.芯间串扰在C+L波段的最大值低于-84.09 dB/100 km,并且弯曲损耗值满足ITU-T建议的G.654光纤在125μm包层直径中对七芯光子晶体光纤的要求.

首都国医名师王沛基于固摄法辨证治疗卵巢癌之经验

文中总结王沛教授基于固摄法治疗卵巢癌之经验。王沛教授认为卵巢癌病因病机为下焦不通-癌毒内生而失固,肝郁肾虚-正气亏虚而耗散,癌毒生长发展而成卵巢癌。肝郁肾虚为卵巢癌之根本病机,外寒、湿热、瘀血、痰饮为卵巢癌形成主要病理因素,癌毒生而失固属卵巢癌发生发展之关键环节。基于“散”与“失固”理论,王沛教授提出了固摄法治疗卵巢癌,以固癌摄瘤防转移,配合攻毒祛邪除癌毒,兼滋肾疏肝固正气为根本原则。并善用虫药,兼顾护脾胃,临床疗效显著。文末附验案1则以佐证。

基于多层水平变化浅海海底模型的低频反演方法

准确获取海底声学参数对声场分析、声纳应用等具有重要意义.反演是获取海底声学参数的重要手段之一.为了避免反演中的多值问题,地声反演往往尽量减少待反演参数,多采用单层或双层水平不变地声模型,反演后的声学参数仅能在有限频段应用,难以同时应用于较宽频段.本文以实验中浅地层剖面仪测量的海底沉积层分层结构为基础建立地声模型,采用多物理量分步联合手段反演各沉积层声学参数,并通过匹配场定位、后验概率分析、采样等手段对反演结果进行验证.将反演结果与单层等效地声模型反演结果进行对比分析,结果说明,本文建立的多层水平变化海底声学参数更接近真实情况,可以应用在较宽频段范围,解释不同声学现象,且精度更高.

分散聚合法制备固井降失水剂及性能研究

针对水溶液聚合以及反相乳液聚合的弊端,首次报道了一种通过分散聚合制备固井降失水剂C-FL72L的方法。其中,以丙烯酰胺(AM)、2-丙烯酰胺基-2-甲基丙磺酸(AMPS)、富马酸(FA)、N,N-二甲基丙烯酰胺(DMA)为聚合单体,季戊四醇三烯丙基醚(APE)为交联剂,聚乙烯吡咯烷酮(PVP-K30)为稳定剂,固含量为33%。对分散聚合的反应动力学进行了考察,反应4 h转化率可达98.9%。通过红外光谱测试、热重分析、高效液相色谱分析、凝胶渗透色谱分析等表征手段,表明所有单体充分且完全聚合,降失水剂耐温超过300℃,分子量可达77.2万。对样品在水泥浆中的应用性能进行了评价,在210℃下,可将失水控制在50 mL以内,水泥浆流变性能、稠化性能、抗压强度等水泥浆综合工程性能良好。并对使用新合成方法制备的降失水剂的作用机理进行了探讨。降失水剂C-FL72L在高密度、低密度、树脂、胶乳、盐水等功能水泥浆体系中综合应用性能优异,有着广阔的应用前景。

一种微结构八边形光子晶体光纤

本文设计了一款微结构八边形光子晶体光纤(PCF),并基于有限元法研究了该结构光纤基模的色散特性、非线性特性及限制损耗特性。研究结果表明:通过适当调节该光纤的结构参数,在波长为1.55μm处,出现了一个零色散点,并且在该波长处,得到高非线性系数值94.97 W^(-1)·km^(-1)以及低限制损耗值3.065×10^(-6)dB/km。该设计为在1.55μm处得到零色散点、高非线性、低损耗的光子晶体光纤提供了理论指导,在色散控制、非线性光学等领域具有潜在的应用前景。

水不分散材料对水泥浆抗水侵性能影响

川渝地区页岩气储层嘉陵江组裂缝性地层发育、地层水活跃,在钻井过程中出现较为突出的漏失问题,对钻井周期产生很大影响,制约了页岩气井的安全高效开采。针对页岩气井出现的漏失问题,对水不分散水泥浆体系进行研究,对5种多糖类聚合物和有机聚合物材料进行水不分散性能评价,优选出关键材料种类及配比,形成适用于含水漏失层封堵的低密度水不分散水泥浆体系,结合平衡压力堵漏工艺,保证水泥浆注替至漏失层后不被地层水冲散,实现漏失地层的有效封堵,为后续施工创造了条件。低密度水不分散水泥浆体系在川渝地区Z203H6-X页岩气漏失井中成功应用,地层承压当量密度由0.99 g/cm^(3)提高到1.21 g/cm^(3),后续结合堵漏浆强化堵漏,地层承压当量密度提升至1.81 g/cm^(3),为川渝地区页岩气井含水裂缝型地层漏失问题提供了一种技术手段。

新安“张一帖内科”痹病辨证思路探析

[目的]总结“张一帖内科”治疗痹病的中医辨证思路。[方法]通过跟诊学习,收集、整理、分析典型医案,查阅相关中医古籍及文献,结合新安医学“张一帖内科”主要传承人国医大师李济仁及李艳教授临证时所谈所述,从痹病病因病机、创新痹病新安理论、临证论治三个方面总结“张一帖内科”治疗痹病的辨证思路与经验,并附医案两则加以佐证。[结果]新安“张一帖内科”创新新安医学理论,创立“平衡寒热、扶元培土”学说,以“寒热三期”疗法治疗痹病,临证注重平调寒热、扶元培土、调和气血、化痰散瘀。验案一中患者反复多关节疼痛,病程长,李艳教授自创“益肾清络活血方”合乌头汤加裁“化痰散瘀”,治疗痰瘀互阻型痹病;验案二中患者劳累过度,湿邪入络,多关节疼痛、肿胀、活动不利,局部有热感,神疲乏力,李艳教授辨证该患者为痹病湿热内阻兼气血亏虚证,以“清热解毒、益气活血通络”平调寒热。[结论]新安“张一帖内科”在治疗痹病实践中形成了自身独特的临床特色,辨证灵活,效果甚佳,是新安医学的重要分支,为中医药治疗痹病拓展了新思路,值得借鉴。

Study of ultraflattened dispersion square-lattice photonic crystal fiber with low confinement loss

A new type ultraflattened dispersion square-lattice photonic crystal fiber with two different air-hole diameters in cladding region is proposed and the dispersion is investigated using a compact 2-D finite difference frequency domain method with the anisotropic perfectly matched layers (PML) absorbing boundary conditions. Through numerical simulation and opti- mizing the geometrical parameters, we find that the photonic crystal fibers proposed can realize ultraflattened dispersion of 0±0.06 ps/(km·nm) in wa...

真空预压加固软土地基变形与固结计算研究

考虑真空度的衰减情况,对真空预压加固软基的变形和固结度计算方法进行了研究。先根据真空预压时砂井的真空压力状态建立了真空预压的空间轴对称变形模型,用位移法推导该模型在等应变条件下的变形及体积应变计算公式。在此基础之上结合Hansbo砂井地基固结理论和真空预压的边界条件,推导了忽略竖向渗流情况下的真空预压加固软土地基的固结解析解。比较文中计算方法与已有计算理论和现场试验实测资料结果表明,体积应变的计算对真空预压的孔压和固结度的计算有较大的影响,而直接引用传统堆载预压的体积应变计算公式计算会导致较大误差。在固结度计算中,采用Hansbo的近似方法能满足计算精度的要求,所得计算结果与实测结果吻合较好。

辽宁牛河梁红山文化遗址土体加固保护材料的筛选

牛河梁遗址是重要的红山文化遗址,为了保护其真实感,决定采用露天保护的方法。由于遗址所处自然环境比较恶劣,需要采用化学材料对遗址进行加固保护。本文采用非水分散体加固剂和有机硅材料对取自牛河梁遗址附近的土样进行了加固试验,通过颜色变化、重量变化、抗压强度、耐水、耐冻融和耐盐试验检验各种材料的加固效果,并将材料进行现场试验,最终确定非水分散体加固剂是土体加固的合适材料。

丙烯酸非水分散体等几种土遗址防风化加固剂的效果比较

对丙烯酸树脂非水分散体等几种土遗址防风化加固剂进行了加固效果对比检验 ,包括加固前后土样各种性能的变化 ,如 :重量、颜色、孔隙率变化 ,抗压强度的提高 ,耐水、耐冻融、耐盐能力的增加等。通过检验发现 ,在所试材料中丙烯酸树脂非水分散体加固剂在浓度非常低的情况下对土体就有加固作用 ,使土体具有很好的耐水性、耐冻融能力 ,耐盐破坏能力也有提高 ,并且不影响土体的外观和透气性。而其它材料如正硅酸乙酯、丙烯酸树脂、聚氨酯、聚酯等虽在一些性能上能满足需要 ,但还有一些方面不能满足要求。对比表明 ,丙烯酸非水分散体是一类优良的土遗址防风化加固剂。

管棚成孔失水引起地表沉降因素分析

利用Biot固结理论,对管棚成孔和推进过程中因渗水而引起的沉降进行计算分析,研究管棚施工时间、管棚数量、不同的管棚直径和地层不同的渗透系数对地表沉降的影响。分析结果表明,若管棚施工从钻孔到注浆的时间控制在2 h以内,则地表最大沉降量小于5 mm;若该时间为8 h,则对应的地表沉降量可达10mm。随着管棚直径的增加,管棚施工中因失水引起的地表沉降量也随之增加。地层渗透系数的大小对沉降量的影响很大。提出控制管棚成孔和推进时间、尽可能地缩短管棚施工时间、采用小直径管棚、管棚施工中采用间隔施工等控制失水沉降的技术措施。

Effect of Cu ion substitution on structural and dielectric properties of Ni-Zn ferrites

A series of Cu-substituted Ni_(0.5-x)Cu_xZn_(0.5)Fe_2O_4(x=0.12,0.16,0.20,0.24 and 0.28) spinel ferrites were prepared by conventional ceramic method to investigate the effects of Cu compositional variation on the structure and dielectric properties.XRD patterns demonstrate that all the samples are crystallized in single-phase cubic spinel structure and the lattice constant increases with increasing Cu content.White grains observed by SEM are Cu-rich phase.The dielectric constant versus frequency curve displays a normal dielectric behavior of spinel ferrites.While the frequency dependence of dielectric loss tangent is found to be abnormal,exhibiting a peak at certain frequency for all Cu-substituted Ni-Zn ferrites.A maximum of the resistivity is observed at x=0.2 due to the decrease of hopping electrons between Fe^(2+) and Fe^(3+) in per unit volume,which is in contrast with the Cu content dependence of dielectric constant and dielectric loss.