双板层角膜移植治疗真菌性角膜溃疡穿孔的临床观察

目的:观察双板层角膜移植治疗真菌性角膜溃疡穿孔的临床效果。方法:回顾性病例研究。收集郑州大学第一附属医院2016年2月至2019年2月真菌性角膜溃疡穿孔40例(40眼)的临床资料。其中病程2周以内者32例,3周~1个月者3例,2个月~2年者5例。有明确的植物性眼外伤史33例,角膜异物剔除术后3例,由手足真菌感染所致者2例,无法说明原因者2例。穿孔直径<2 mm者37例,2~4 mm者3例。所有患者分成两组,结膜瓣遮盖组及角膜双板层移植组。每组20例,供体角膜系甘油保存者。记录两组视力及角膜植片情况。结果:术后随访0.5~2年,结膜瓣组视力光感14例,手动4例,数指2例。角膜移植组外植片透明,内植片轻度浑浊,视力光感2例,手动3例,数指12例,0.1~0.2者2例,>0.2者1例。1例植片浑浊真菌复发,1例发生排斥。结论:双板层角膜移植治疗真菌性角膜溃疡穿孔,视力恢复较好。

自体角膜转位移植联合双板层角膜移植治疗角膜穿孔效果评价

目的评价自体角膜转位联合双板层角膜移植术治疗角膜穿孔的临床效果。方法对2010年6月至2012年12月因角膜穿孔而实施自体角膜转位联合双板层角膜移植术的8例（8只眼）进行了回顾性分析。其中真菌性角膜溃疡穿孔5只眼，铜绿假单胞菌性角膜溃疡穿孔1只眼，角膜Mooren溃疡穿孔1只眼，圆锥角膜急性穿孔1只眼。结果所有患者眼表形态结构均得到有效的恢复，避免了摘除眼球，5只眼保留了有效视力，其中术后1个月矫正视力：手动3只眼，0．04者2只眼，0．05者1只眼，0．08者1只眼，0．1者1只眼。术后14d内8只眼角膜植片上皮均愈合完整，角膜植片与植床对合好。所有患者术后短期内均无其他并发症。结论自体角膜转位联合双板层角膜移植术治疗角膜穿孔安全有效，在缺少角膜供体材料的情况下，是一种有效挽救眼球的治疗方法。

双板层角膜移植对高危角膜移植患者疗效观察

目的 观察双板层角膜移植对高危角膜移植患者的治疗效果.方法 回顾性病例系列研究.选取2008年1月至2012年6月在南华大学附属第二医院接受手术的高危角膜移植患者25例（男性15例,女性10例）,并按术式不同分为两组：双板层角膜移植组8例（男性5例,女性3例）;穿透性角膜移植组17例（男性10例,女性7例）.术后定期复查裸眼视力、眼压、眼底及裂隙灯检查;术后1、3、6、12个月行验光（查矫正视力）及角膜内皮细胞计数检查.采用秩和检验比较两组患者术前裸眼视力;采用Fisher确切概率法检验比较两组患者排斥反应发生率;采用t检验比较两组患者年龄、术后裸眼视力、矫正视力、眼压及角膜内皮细胞密度.结果 双板层角膜移植组患者平均年龄（43.6±16.5）岁,术前视力为FC/20 cm～0.1;穿透性角膜移植组患者平均年龄（45.3±15.7）岁,术前视力为FC/20 cm～0.08.两组患者年龄及术前视力比较差异无统计学意义（t=1.322,P=0.199;t=116.5,P =0.264）.双板层角膜移植组裸眼视力在术后1、3、6、12个月均优于穿透性角膜移植组,差异比较有统计学意义（P＜0.05）;矫正视力：术后1个月双板层角膜移植组较穿透性角膜移植组差异有统计学意义（t =2.637,P=0.014）,术后3、6个月两组差异比较无统计学意义（t=1.544、1.592,P =0.137、0.135）,术后1年双板层角膜移植组优于穿透性角膜移植组差异有统计学意义（t=2.216,P =0.038）.两组患者角膜内皮细胞密度均呈明显下降趋势,但双板层角膜移植组角膜内皮细胞密度下降较穿透性角膜移植组缓慢.术后1、3、6、12个月双板层角膜移植组角膜内皮细胞密度均高于穿透性角膜移植组,两组差异比较有统计学意义（P＜0.05）.穿透性角膜移植组有2例在手术后1个月内发生继发性青光眼,双板层角膜移植组均无病例发生.手术后1年内穿透性角膜移植组共有6例发生排斥反应,发生率为35.3％ （6/17）;双板层角膜移植组有2例发生排斥反应,发生率为25％ （2/8）,两组差异比较无统计学意义（P =0.487）.经抗排斥处理,穿透性角膜移植组有4例排斥反应被控制,2例角膜植片出现混浊;双板层角膜移植组2例排斥反应均被控制,植片恢复透明.结论 对于高危角膜移植患者,双板层角膜移植较穿透性角膜移植视力恢复理想,内皮细胞密度下降缓慢,排斥反应发生率低,但仍需要大样本及长时间的观察来进一步证实.

Shear resistance performance of steel-concrete-steel composite shear wall

For a deeper understanding of the shear resistance performance of the steel-concrete-steel composite shear wall, the main influence factors such as the thicknesses of the steel plates and the concrete, the strength grades of the concrete and the span-depth ratios of the composite wall, which have impacts on the shear resistance performance of the composite shear wail, are analyzed by the numerical simulation method. Meanwhile, the simplified calculation formulae of the initial elastic lateral-resisting stiffness and the shear bearing capacity of the composite shear wall are also proposed. The research shows that with the increase in the thicknesses of the steel plates and the concrete and the increase in the strength grades of the concrete, the shear performance of the shear wall improves obviously; the span-depth ratios of the composite wall have a significant effect on the initial elastic lateral- resisting stiffness, but a small effect on the shear bearing capacity. Comparing the results of the simplified calculation formulae with those of the nonlinear finite element method, it is obvious that the presented formulae are reasonable and meet the real force state of the structure. These conclusions can serve as a preliminary design reference for the steel-concrete- steel composite shear wall.

Experimental investigation on heat transfer characteristics of a new radiant floor system with phase change material

In order to improve the heat transfer characteristics of the traditional phase change material（PCM） floor, a new double-layer radiant floor system with PCM is proposed, which can store thermal or cold energy in the off-peak period and use them in the peak period. An experimental setup was developed to study the heat transfer characteristics of the new system under both cooling and heating modes. The experimental results show that the double-layer radiant floor system with PCM can meet both the cold and thermal requirements of users. Moreover, with the same duration of the thermal energy storage process, the increase of water temperature supplied to the system can improve the heat transfer characteristics of the system but lead to the discomfort of users. On the other hand, if the air temperature at the end of the thermal energy storage process is the same under different conditions, the increase of supplied water temperature will decrease the thermal energy storage time and ensure the comfort of users.

Butt joining of Al-Cu bilayer sheet through friction stir welding

Butt joining of Al–Cu bilayer sheet produced by cold roll bonding was studied through friction stir welding (FSW). A defect free joint was obtained. Flow patterns and mixing of two layers during FSW were investigated. Microstructural investigations and hardness profile measurements were carried out. It is shown that material flow in stir zone leads to the formation of banding structure in Cu layer at advancing side. Traces of Al particles along with Al–Cu intermetallic compounds exist in the fined grain region of this banding structure which leads to higher hardness values.

Hydrodynamic deep drawing of double layered conical cups

Hydrodynamic deep drawing assisted by radial pressure is an advanced sheet forming technology with great advantages such as higher drawing ratio, good surface quality and higher dimensional accuracy. In this process, both the bottom surface and the peripheral edge of sheets are under hydrodynamic pressure, so that the forming procedure is more uniform with low failure probability. Multi-layered sheets with complex geometries could be formed more easily with this technique compared with other traditional methods. Rupture is the main irrecoverable failure form in sheet forming processes. Prediction of rupture occurrence is of great importance for determining and optimizing the proper process parameters. In this research, a theoretical model was proposed to calculate the critical rupture pressure in production of double layered conical parts with hydrodynamic deep drawing process assisted by radial pressure. The effects of other process parameters on critical rupture pressure, such as punch tip radius, drawing ratio, coefficient of friction, sheet thickness and material properties were also discussed. The proposed model was compared with finite element simulation and validated by experiments on Al1050/St13 double layered sheets, where a good agreement was found with analytical results.

Variation analysis of ultimate pullout capacity of shallow horizontal strip anchor plate with 2-layer overlying soil based on nonlinear M-C failure criterion

Based on the nonlinear Mohr-Coulomb failure criterion and an associated flow rule,a kinematic admissible velocity field of failure mechanism of the 2-layer soil above a shallow horizontal strip anchor plate is constructed.The ultimate pull-out force and its corresponding failure mechanism through the upper bound limit analysis according to a variation principle are deduced.When the 2-layer overlying soil is degraded into single-layer soil,the model of ultimate pullout force could also be degraded into the model of single-layer soil.And the comparison between results of single-layer soil variation method and those calculated by rigid limit analysis method proves the correctness of our method.Based on that,the influence of changes of geotechnical parameters on ultimate pullout forces and failure mechanism of a shallow horizontal strip anchor with the 2-layer soil above are analyzed.The results show that the ultimate pull-out force and failure mechanism of a shallow horizontal strip anchor with the 2-layer soil above are affected by the nonlinear geotechnical parameters greatly.Thus,it is very important to obtain the accurate geotechnical parameters of 2-layer soil for the evaluation of the ultimate pullout capacity of the anchor plate.

Plate reinforced square hollow section X-joints subjected to in-plane moment

The static test of 13 square hollow section(SHS) X-joints with different β and different types of plate reinforcement under in-plane moment in brace was carried out. Experimental test schemes, failure modes of specimens, moment-vertical displacement curves, moment-deformation of the chord, and strain strength distribution curves were presented. The effect of β and plate reinforcement types on in-plane flexural property of SHS X-joints was studied. Results show that punching shear of chord face disappears, brace material fracture appears and concave and convex deformation of chord decrease when either collar plates or doubler plates were welded on chord face. Moment-vertical displacement curves of all specimens have obvious elastic, elastic-plastic and plastic stages. As β increases, the in-plane flexural ultimate capacity and initial stiffness of joints of the same plate reinforcement type increase, but ductility of joints decreases. With the same β, the in-plane flexural initial stiffness and ultimate capacity of doubler plate reinforced joints, collar plate reinforced joints, and unreinforced joints decrease progressively. Thickness of reinforcement plate has no obvious effect on in-plane flexural initial stiffness and ultimate capacity of joints. As thickness of reinforcement plate increases, the ductility of reinforced X-joints decreases. The concave and convex deformation of every specimen has good symmetry;as β increases, the yield and ultimate deformation of chord decrease.

Influence of lateral pressure on mechanical behavior of different rock types under biaxial compression

Lots of field investigations have proven that layer-crack structure usually appears during the excavation process of deep rock or coal mass.To provide experimental data for studying the formation mechanism of layer-crack structure,this study researches the influence of lateral pressure on the mechanical behavior of different rock types.Four rock types have been tested and the formation mechanism of macro-fracture surface is analyzed.Results indicate that the brittleness and burst proneness of rock or coal material are stronger than that of gypsum material due to the different mineral compositions and structures.When the lateral pressure is less than 10%uniaxial strength,the peak stress and elastic modulus increase with the increase of lateral pressure;but when the lateral pressure is larger than 10%uniaxial strength,the two parameters decrease slightly or keep steady.This is because when the lateral pressure reaches a certain value,local failure will be formed during the process of applying lateral pressure.Under the condition of low lateral pressure,the failure of the specimen is dominated by the tensile mechanism;under the condition of relatively high lateral pressure,the area of the specimen close to the free surface is tensile splitting failure,and the area far from the free surface is shear failure.

Mathematical modeling on multi-stage series crushing ratio distribu- tion based on fuzzy physical programming

Double-layer, multi-roller plate crusher is a new device, that uses a multi-stage series crushing style to break particles, with the crushing ratio distribution directly influencing the machine＇s performance. Three crushing ratios of 2.25, 2.15 and 2.01, used for fuzzy physical programming, were determined. The comparison of the optimized result between the double-layer multi-roller plate crusher and a high pressure roll grinder showed that the double-layer multi-roller plate crusher had a better performance, reducing crushing force and wear.

Penetration of disk fragments following impact on thin plate

To investigate the ballistic resistance and failure pattern of aeroengine casing following the impact of disk fragments, and to determine the optimum case structure, the phenomena of a 1/3rd disk fragment impact on single and double-layered thin plate targets were simulated using nonlinear dynamical analysis software MSC.Dytran. Strain rate effect was introduced in a Johnson-Cook (JC) material model for the disk fragment and the plate. Impact modeling was based on the Arbitrary Lagrange-Eulerian method, and simulated using explicit finite element method (FEM). Simulation results showed that the major failure pattern of the plate is shearing and tensile fracture with large plastic deformation. It was also concluded that the ballistic limit velocity increases with the standoff distance when it is beyond a certain value, and that greater resistance is obtained when the front plate has either a proportionately low or high thickness. The impact resistance of a double-layered plate may exceed that of a single plate if the thicknesses and standoff distance of the two plates are set appropriately.