彩板与C型檩条共同作用下屋面系统承载力的变化

分析了Ｃ型截面檩条在风吸力下的变形和承地菌，同时考虑屋面板的约束作用及檩条的初始侧向弯曲对檩条的影响，研究初始侧向弯曲偏向何方对结构有利；确定了檩条开口方向的组合方式。     

发散冷却叶片叶栅试验

通过长期运行,考核冷却孔设计,骨架和蒙皮强度是否适用,蒙皮抗堵塞性能,蒙皮与骨架的焊接性能,以及试验台对高温试验的适应性。经210h试验,上述目的全部完成。证明发散冷却叶片用于航空发动机做导向叶片是完全可行的。     

连续Z型檩条的应用设计

结合实际对连续Z型檩条的设计选用、节点连接进行探讨,使冷弯薄壁型钢檩条的设计更加经济合理。     

酒钢热电技改工程厂房墙面大跨距檩条的荷载验算

本文主要通过对热电技改工程厂房墙面大跨距檩条的荷载验算,初步证明在嘉峪关地区的轻钢结构围护檩条跨距可以由传统的6 m提高到8 m。     

轻钢结构特点以及发展趋势

本文简要介绍当今正蓬勃发展的轻钢结构的概况,对它的适用范围、主要优点、材料造型和设计中的注意点,均作了扼要介绍,对屈曲后强度利用、蒙皮效应等与一般钢结构设计的不同点作了相应提示.使对轻钢结构的特点有一较为完整的认识.     

发散气冷叶片蒙皮材料的研究

本文研究了发散气冷叶片丝网蒙皮用材料及其拉丝、编网工艺的选取原则,以及多孔蒙皮材料本身的抗张强度和抗氧化性能。确定了压下量对多孔蒙皮材料透气性能和各种物理性能的影响。研究了清洗和烧结工艺对多孔蒙皮材料抗张强度、晶粒度和扩散粘合性能的影响。初步建立了烧结后多孔蒙皮材料的质量检验标准。用该材料做成叶片进行叶栅试验指出,相对冷效系数(1—φ)可达0.4～0.6范围,这一结果接近国外同类试验水平。     

高强度低成本Ti5322合金的抗弹性能及其抗弹机理研究

采用底推式105 mm长杆穿甲模拟弹,对厚度为45 mm的高强度低成本Ti5322合金靶板开展了终点弹道侵彻实验,研究了该合金的抗弹性能与抗弹机理,并探究了合金的典型抗弹效应——倾角效应。结果表明,Ti5322合金的质量防护系数为1.80,空间防护系数为1.02。Ti5322合金的损伤机制和抗弹机理是通过自身的绝热剪切局域化行为实现的。这种绝热剪切局域化行为,一方面通过靶板的变形破碎协调了弹体侵入过程的挤凿作用;另一方面,弹靶作用过程中发生的弹靶互侵蚀行为有效地消耗了弹体动能。     

钛会论文 高强度低成本Ti5322钛合金的抗弹性能及其抗弹机理研究

本文开展了高强度低成本Ti5322钛合金的抗弹性能及其抗弹机理研究,通过采用底推105长杆形穿甲模拟弹丸,对厚度为45mm的均质Ti5322钛合金靶板开展终点弹道侵彻实验,研究了高强度低成本Ti5322钛合金在长杆形穿甲弹丸侵彻条件下的抗弹性能及其抗弹机理,并探究了该低成本钛合金的典型抗弹效应：倾角效应。结果表明,高强度低成本Ti5322钛合金的质量防护系数高达1.80,和均质装甲钢相比提高了80％；其空间防护系数和均质装甲钢相当,约为1.02。结合损伤后靶板的宏微观损伤分析,发现：在长杆形穿甲弹丸的侵彻条件下,高强度低成本Ti5322钛合金的损伤机制和抗弹机理是通过自身的绝热剪切局域化行为实现的；这种Ti5322钛合金靶板的绝热剪切局域化行为,一方面,通过靶板的变形破碎协调了弹体侵入过程的挤凿作用；另一方面,弹靶作用过程中发生的弹靶互侵蚀行为有效的消耗了弹体动能。对高强度低成本Ti5322钛合金倾角效应的研究发现,在长杆形穿甲弹丸的侵彻条件下,Ti5322钛合金的倾角效应表现为正效应,这是因为,随着弹丸侵彻角度的增大,在弹靶作用初期就发生了严重的弹靶互侵蚀行为。     

2A12合金化铣样品表面粗晶形成机理研究

2A12铝合金广泛应用于机身蒙皮等飞机结构件.拉伸成形(拉形)是蒙皮类零件成形的重要加工工艺,在拉形过程及后续处理中出现的表面缺陷将严重影响蒙皮的使用寿命.通过宏观观察、化学成分、显微组织分析等检测手段对化铣后表面出现的粗晶现象的2A12铝合金样品进行了综合分析,认为样品粗大晶粒是在预拉形后的淬火热处理过程中形成的,并...     

轻钢结构设计工作中值得注意的问题

本文对轻钢结构的适用范围、主要优点、材料选型作了扼要介绍，总结了轻钢结构的支撑设置、檩条计算、拉条设置、拉条节点等几方面设计中常见问题，并加以分析，以期使设计人员更好地掌握轻钢结构设计。     

Topical silicone gel sheeting in the treatment of hypertrophic scars and keloids. A dermatologic experience

BACKGROUND: Topical silicone gel sheeting has been used successfully in the management of hypertrophic and keloid scars resulting from thermal burn wounds. METHODS: An open-labelled approach using the silicone gel sheets was performed using hypertrophic and keloid scars secondary to surgical procedures or traumatic insults. RESULTS: The silicone gel sheets resulted in moderate improvement in scar thickness, scar color and was noted to be effective to some degree in all tested. The material was easy to use and painless. CONCLUSION: Topical silicone gel sheeting is an effective method for the treatment of hypertrophic and keloid scars and may be considered useful in the treatment of these difficult cutaneous lesions.     

Stiffness and Strength of Metal Bridge Deck Forms

Light gauge metal sheeting is often utilized in the building and bridge industries for concrete formwork. Although the in-plane stiffness and strength of the metal forms are commonly relied upon for stability bracing in buildings, the forms are generally not considered for bracing in steel bridge construction. The primary difference between the forming systems in the two industries is the method of connection between the forms and girders. In bridge construction, an eccentric support angle is incorporated into the connection details to achieve a uniform slab thickness along the girder length. While the eccentric connection is a benefit for slab construction, the flexible connection limits the amount of bracing provided by the forms. This paper presents results from the first phase of a research study investigating the bracing behavior of metal bridge deck forms. Shear diaphragm tests were conducted to determine the shear stiffness and strength of bridge deck forms, and modified connection details were developed that substantially improve the bracing behavior of the forms. The measured stiffness and strength of diaphragms with the modified connection often met or exceeded the values of diaphragms with conventional noneccentric connections. The experimental results for the diaphragms with the modified connection details dramatically improve the potential for bracing of steel bridge girders by metal deck forms.     

Effect of Intermediate Diaphragms on Decked Bulb-Tee Bridge System for Accelerated Construction

One of the promising systems for accelerated bridge construction is the use of the decked precast prestressed concrete girders or decked bulb-tee girders for the bridge superstructure. Using the calibrated three-dimensional finite-element models through field tests, a parametric study was conducted to determine the effect of intermediate diaphragms on the deflections and flexural strains of girders at the midspan as well as the live load forces in the longitudinal joint. The following diaphragm details were considered: different diaphragm types (steel and concrete), different diaphragm numbers between two adjacent girders, and different cross-sectional areas for steel diaphragms. Five bridge models with different diaphragm details were developed, and the short span length effect on the bridge behavior was also studied. It was found that as long as one intermediate diaphragm was provided between two adjacent girders at midspan, changing the diaphragm details did not affect the girder deflection, the girder strain, and the live load forces in the longitudinal joint significantly. The effect of diaphragms on the midspan deflection was more prominent in the short span bridge; however, the reduction in the maximum bending moment by the diaphragms was more significant in the long span bridge than in the short span bridge. Specific design recommendation is provided in this paper.     

Strength and Behavior of Hybrid Diaphragms

Advantages of diaphragms using glass fiber-reinforced polymer (GFRP) panels in conjunction with plywood panels as sheathing (hybrid diaphragms) are presented in this paper. The strength and behavior of individual connections between GFRP sheathing panels and wood framing are determined through coupon testing. Coupon test results indicate that GFRP sheathing-to-framing connections have significant increases in strength, stiffness, and energy absorption. The strength and behavior of hybrid diaphragms are determined by testing a conventional diaphragm (wood sheathing only) and a hybrid diaphragm. The hybrid diaphragm sustained 34% more load compared to the conventional diaphragm.     

Live-Load Distribution Factors in Prestressed Concrete Girder Bridges

This paper presents an evaluation of flexural live-load distribution factors for a series of three-span prestressed concrete girder bridges. The response of one bridge, measured during a static live-load test, was used to evaluate the reliability of a finite-element model scheme. Twenty-four variations of this model were then used to evaluate the procedures for computing flexural live-load distribution factors that are embodied in three bridge design codes. The finite-element models were also used to investigate the effects that lifts, intermediate diaphragms, end diaphragms, continuity, skew angle, and load type have on distribution factors. For geometries similar to those considered in the development of the American Association of State Highway and Transportation Officials Load and Resistance Factor Design Specifications, the distribution factors computed with the finite-element models were within 6% of the code values. However, for the geometry of the bridge that was tested, the discrepancy was 28%. Lifts, end diaphragms, skew angle, and load type significantly decreased the distribution factors, while continuity and intermediate diaphragms had the least effect. If the bridge had been designed using the distribution factors calculated with the finite-element model rather than the code values, the required concrete release strength could have been reduced by 6.9 MPa (1,000 psi) or the live load could have been increased by 39%.     

Static-electric field induction by a silicone cushion for the treatment of hypertrophic and keloid scars

Silicone gel and silicone occlusive sheeting are widely used at present for the treatment of hypertrophic and keloid scars, without any scientific explanation as to their mode of action. In a recent paper the possibility was raised that static electricity generated by friction-activated silicone sheeting could be the reason for this effect, and that it can, with time, cause involution of hypertrophic and keloid scars. The objective of this study was to test this hypothesis and to observe whether a continuous and also an increased negatively charged static-electric field will shorten the treatment period. A device to implement these requirements gradually evolved over a 5-year period. A number of prototypes were tested until the final product was attained. Some of the patients in this study were treated initially with a silicone sponge inserted in the cushion. Later this version was changed to the final design described herein. A silicone cushion was developed with the purpose of increasing a negative static-electric charge to accelerate the regression process. The cushion is custom-made using a silicone occlusive sheeting envelope of 0.75-mm thickness, which does not deteriorate with use, and is partially filled with high viscosity silicone oil. Its edges are sealed, and its size is designed to extend a little beyond the scarred area. Static electricity readings, generated by activating the cushion by pumping action with the fingers, stretching or deforming the cushion, are invariably much higher when compared with those obtained with silicone occlusive sheeting and silicone gel sheeting. The interaction between the negatively charged ions of the cushion and the ionic charges of the tissue fluids may be the critical factor in achieving hypertrophic and keloid scars involution. Of the 30 patients enrolled in the study, 3 patients dropped out. Treatment with the silicone cushions yielded 63.3 percent cessation of itching and burning followed by pallor and flattening of the scar, some markedly so, over a few weeks to 6-month period. An additional 26.6 percent had their scars resolved in up to 12 months of treatment. Good contact of the cushion over the scar has been shown to be important in this clinical trial, and much creativity is needed for making elastic strap bindings that ensure this contact. The clinical trials extended over a 12-month period. Ten patients (33.3 percent) who had recalcitrant scars with little response to the use of the silicone cushion were given intralesional corticosteroid injections, in addition to the continued use of the cushion, resulting in a fairly rapid resolution of these scars over a period of months to a year.     

Full-Scale Test of Continuity Diaphragms in Skewed Concrete Bridge Girders

Continuity diaphragms used in prestressed girder bridges on skewed bents have caused difficulties in detailing and construction. The results of the field verification for the effectiveness of continuity diaphragms for skewed, continuous, and prestressed concrete girder bridges are presented. The current design concept and bridge parameters that were considered include skew angle and the ratio of beam spacing to span (aspect ratio). A prestressed concrete bridge with continuity diaphragms and a skewed angle of 48° was selected for full-scale test by a team of engineers from Louisiana Department of Transportation and Development and the Federal Highway Administration. The live load tests performed with a comprehensive instrumentation plan provided a fundamental understanding of the load transfer mechanism through these diaphragms. The findings indicated that the effects of the continuity diaphragms were negligible and they can be eliminated. The superstructure of the bridge could be designed with link slab. Thus, the bridge deck would provide the continuity over the support, improve the riding quality, enhance the structural redundancy, and reduce the expansion joint installation and maintenance costs.     

Susceptibility of Aspergillus strains from culture collections to amphotericin B and itraconazole

BACKGROUND: Over the last decade the benefits of occlusive dressings have been appreciated. These dressings allow the epithelium to resurface easier. The wound heals quicker. OBJECTIVE: To evaluate a new silicone sheeting for immediate post-op wound care. Our objective was to determine its benefit in the wound care management after laser skin resurfacing. METHOD: The silicone sheeting was applied immediately after laser resurfacing in 35 individuals. This temporary skin replacement was held in place with 4 x 4 gauzes and tube gauze netting. Although the tube netting and the 4 x 4 gauzes were changed daily the silicone sheeting remained in place for 4 or 5 days. Following this, applications of a petrolatum-based ointment were continued for another 5 days. At day 10 the skin care program was changed to a moisturizing sunscreen. Bleaching cream was added at day 15 in darker complexed individuals. RESULTS: The dressing accelerated wound healing. Pain and swelling were minimized under the sheeting. Histologic examinations demonstrated a more rapid reepithelialization at these treated sites. Other than technical problems, such as the riding up of the dressing over the jawline or retraction of the dressing off the lips or off the eyelids, there were no adverse sequelae. The wound healed rapidly and allowed the rapid progression to the application of a moisturizer-sunscreen or a skin-bleaching cream. Other than these technical problems there were no complications. No wound infections were noted. CONCLUSION: The use of silicone sheeting following skin resurfacing facilitated a rapid reepithelialization of treated areas. There was a remarkable reduction in erythema and edema accompanying the use of the dressing. The program made it possible for patients to return to work in 12-15 days.     

Anchorage of External Tendons in End Diaphragms

External posttensioning tendons in concrete box girder bridges are usually anchored in very massive end diaphragms. Several incidences of distress of such diaphragms have been reported in the literature. This paper presents the results of an analytical and experimental research program on design and behavior of end diaphragms when used for the anchorage of external tendons. Finite-element analysis results, strut-and-tie models, and results of a physical test series of half-scale specimens are included. The strut-and-tie model approach is shown to be an effective method to describe the flow of forces in the structure and for design. Ultimate strength predictions based on simple strut-and-tie models were safe but quite conservative. Refined strut-and-tie models based on finite-element analysis results were required to arrive at satisfactory reinforcement arrangements for crack control.     

Girder Differential Deflection and Distortion-Induced Fatigue in Skewed Steel Bridges

The prevalence of fatigue cracking in steel bridge girders due to out-of-plane web distortion motivates development of procedures to evaluate the effects of distortional fatigue. In a previous study sponsored by the Minnesota Department of Transportation (Mn/DOT) the frequency and magnitude of distortional stresses on a typical skewed, steel bridge with staggered, bent-plate diaphragms were assessed. The results revealed a diaphragm deformation mechanism that causes distortional fatigue in the girder web gap, leading to simple, accurate estimates of fatigue stress if bridge properties and differential vertical deflection between girders are known. In the present study, linear finite element models are used to represent composite steel bridges and identify bridge parameters that influence relative deflection of adjacent girders. Parameters found to have a significant effect on differential deflection include girder spacing, angle of skew, span length, and deck thickness. These results are incorporated in a simple procedure that is intended for use in management schemes for skewed, steel-girder bridges, with staggered, bent-plate diaphragms, susceptible to web gap distortional fatigue.