A shield of defense:Developing ballistic composite panels with effective electromagnetic interference shielding absorption

The primary goal of this study is to develop cost-effective shield materials that offer effective protection against high-velocity ballistic impact and electromagnetic interference(EMI)shielding capabilities through absorption.Six fiber-reinforced epoxy composite panels,each with a different fabric material and stacking sequence,have been fabricated using a hand-layup vacuum bagging process.Two panels made of Kevlar and glass fibers,referred to as(K-NIJ)and(G-NIJ),have been tested according to the National Institute of Justice ballistic resistance protective materials test NIJ 0108.01 Standard-Level IIIA(9 mm×19 mm FMJ 124 g)test.Three panels,namely,a hybrid of Kevlar and glass(H-S),glass with ceramic particles(C-S),and glass with recycled rubber(R-S)have been impacted by the bullet at the center,while the fourth panel made of glass fiber(G-S)has been impacted at the side.EMI shielding properties have been measured in the X-band frequency range via the reflection-transmission method.Results indicate that four panels(K-NIJ,G-NIJ,H-S,and G-S)are capable of withstanding high-velocity impact by stopping the bullet from penetrating through the panels while maintaining their structural integrity.However,under such conditions,these panels may experience localized delamination with variable severity.The EMI measurements reveal that the highest absorptivity observed is 88% for the KNIJ panel at 10.8 GHz,while all panels maintain an average absorptivity above 65%.All panels act as a lossy medium with a peak absorptivity at different frequencies,with K-NIJ and H-S panels demonstrating the highest absorptivity.In summary,the study results in the development of a novel,costeffective,multifunctional glass fiber epoxy composite that combines ballistic and electromagnetic interference shielding properties.The material has been developed using a simple manufacturing method and exhibits remarkable ballistic protection that outperforms Kevlar in terms of shielding efficiency;no bullet penetration or back face signature is observed,and it also demonstrates high EMI shielding absorption.Overall,the materials developed show great promise for various applications,including the military and defense.

Correlation between induced embryo toxicity and absorption dose of enriched uranium in testes

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Effect of water absorption ratio on tensile strength of red sandstone and morphological analysis of fracture surfaces

Brazilian disc tests were undertaken on a number of red sandstone samples with different water absorption ratios.The tensile strength of the red sandstone decreases as the water absorption ratio increases.The fracture surfaces of failed red sandstone discs were scanned by Talysurf CLI 2000.With the aid of Talymap Gold software,based on ISO25178,a set of statistical parameters was obtained for the fracture surfaces.The maximum peak height(S_p),maximum pit height(S_v) and maximum height(S_z) of the fracture surfaces exhibited the same decreasing trend with increasing water absorption.Sa and Sku values for the fracture surfaces showed a downward trend as the water absorption ratio increased.The fractal dimensions of fracture surfaces were calculated and found to decrease as the water absorption ratio increased.Through analysis of PSD curves,the smallest dominant wavelength was observed to reflect the roughness of the fracture surfaces.Additionally,the results suggest that the roughness of fracture surfaces becomes small as the water absorption ratio increases.

Experimental Study on the Energy Absorption Properties of MWK Reinforced Composites

The energy absorption properties of MWK fabric reinforced composite plates were studied. Low velocity and low energy impact experiments were carried out for MWK fabric reinforced Glassfibre/Epoxy composite plate, by setting up a drop weight impact test system. Using this system, the drop weight velocity during impacting was obtained and recorded by transducer and corresponding signal processing system. Based on the velocity record, the impact energy and dissipated impact energy (energy absorption) were obtained. The influences of structure parameters of MWK on the impact behavior and energy absorption properties were then investigated.

Energy Absorption of Pultruded Glass-Graphite/Epoxy Hybrid Composites under High Strain-Rate Induced Transverse Tension

This paper focuses on the dynamic tensile response of glass-graphite/epoxy composites illustrating improvement in energy absorption through hybridization. The dynamic response and energy absorption characteristics of pultruded hybrid combinations of glass and graphite fibers in an epoxy matrix subjected to induced transverse tension at high strain-rate in a modified Split Hopkinson Pressure Bar (SHPB) apparatus, are presented. Transverse tensile strength was determined by diametral compression of disc samples (Brazilian indirect tensile test method). Diametral crack initiation and strain to failure were monitored with a Shimadzu HPV-2 high-speed video camera at a recording speed of 500,000 fps and Digital Image Correlation (DIC). Adequate measures were taken to ensure that initiation of specimen failure occurred at the exact center of the disc specimen, and propagated through the diameter along the compressive loading axis, for the induced transverse tension tests to be valid. A study of the strength and specific energy absorption demonstrates the benefits of hybridization. Under induced transverse tensile loading condition, the pure glass/epoxy (GL60) exhibited higher strength than pure graphite/epoxy (GR60). Pure graphite/epoxy (GR60) has higher specific energy absorption capacity than pure glass/epoxy (GL60) in transverse tension. Among all hybrids, GR30 has the highest specific energy absorption under transverse tension. Overall, hybrid GL48, with 48% low-cost glass fibers in the inner core and 12% high-cost graphite fibers in outer shell, was found to exhibit better performance under induced transverse tension at high strain-rates, showing the benefits of hybridization.

Effect of dynamic loading conditions on the dynamic performance of MP1 energy-absorbing rockbolts:Insight from laboratory drop test

Energy-absorbing rockbolts have been widely adopted in burst-prone excavation support, and their serviceability is closely related to the frequency and magnitude of seismic events. In this research, the splittube drop test with varying impact energy was conducted to reproduce the dynamic performance of MP1rockbolts under a wide range of seismic event magnitudes. The test results showed that the impact process could be subdivided into four distinct stages, i.e. mobilization, strain hardening, plastic flow(ductile), and rebound stage, of which strain hardening and plastic flow are the primary energy absorbing stages. As the impact energy per drop increases from 8.1 to 46.7 k J, the strain rate of the shank varies between 1.20 and 2.70 s^(-1), and the average impact load is between 240 and 270kN, which may be considered as constant. The MP1 rockbolt has a cumulative maximum energy absorption(CMEA) of 31.9–40.0 k J/m, with an average of 35.0 k J/m, and the elongation rate is 11.4%–14.7%, with an average of 12.7%, both of which are negatively correlated with the impact energy per drop. Regression analysis shows that energy absorption and shank elongation, as well as momentum input and impact duration,conform to the linear relationship. The complete dynamic capacity envelope of MP1 rockbolts is proposed, which reflects the dynamic bearing capacity, elongation, and distinct stages. This study is helpful to better understand the dynamic characteristics of energy-absorbing rockbolts and assist design engineers in robust reinforcement systems design to mitigate rockburst damage in seismically active underground excavations.

Analytical method for promoting process capability of shock absorption steel

Mechanical properties and low cycle fatigue are two factors that must be considered in developin gnew type steel for shock absorption. Process capability and process control are significant factors in achieving the purpose of research and development programs. Often-used evaluation methods failed to measure processyield and process centering ; so this paper uses Taguchi loss function as basis to establish an evaluation methodand the steps for assessing the quality of mechanical properties and process control of an iron and steel manu-facturer. The establishment of this method can serve the research and development and manufacturing industry and lay a foundation in enhancing its process control ability to select better manufacturing processes that are more reliable than decision making by using the other commonly used methods.

双壳体核电厂空间减震结构的竖向动力试验研究

为降低核电厂内安全壳的竖向加速度,提出了一种双壳体空间减震结构,基于该结构的力学特性建立了简化三质点三自由度动力模型,进一步给出了结构响应传递函数并进行了参数分析,明确了结构质量比、阻尼比和频率比对结构竖向地震响应的影响规律,完成了双壳体空间减震结构的缩尺振动台动力试验。结果表明:双壳体空间减震结构可减小内安全壳的竖向加速度,减震率为12.23%~27.84%。双壳体空间减震结构的振动台试验响应结果与理论计算值吻合较好,验证了所提出的双壳体空间减震结构简化模型的准确性以及双壳体空间减震系统的有效性。

过滤吸油用PP/PE双组分熔喷非织造布的性能测试研究

以不同质量比的聚丙烯(PP)、聚乙烯(PE)为原料制得PP/PE双组分熔喷非织造布,测试分析了PP/PE双组分熔喷非织造布的性能。结果表明:PP/PE双组分熔喷非织造布的纤网呈现蓬松杂乱的三维结构,纤维直径较细,孔隙率较高;随着PE添加比例增大,PP/PE双组分熔喷非织造布的面密度和厚度增大,拉伸断裂强力、顶破强力略有下降,硬挺度下降,透气性增大;当PP/PE质量比为73时,PP/PE双组分熔喷非织造布的水接触角在129°左右,吸油倍数为18.75,20 s内吸油高度为1.7 mm,空气过滤效率为56.82%,综合性能较好,可应用于过滤、吸油等领域。

同种抗-C、e伴类同种抗-e、Jk b自身抗体的鉴定及输血治疗

目的应用吸收放散和效价积分法对1例抗-C、e同种抗体合并抗-e、Jk b类同种自身抗体进行鉴别诊断。方法采用试管法对ABO、Rh和Kidd血型抗原进行鉴定;盐水、凝聚胺、微柱凝胶3种方法联用2套谱细胞进行抗体筛查及抗体特异性鉴定;多重吸收放散试验和效价积分原则对抗体进一步确认;多重PCR技术对RHCE基因、JK基因进行测序。结果通过血清学分析,该患者血型为A型、Rh分型ccDEE,直抗阳性。结合不同的Rh和Jk表型细胞吸收放散试验以及效价积分原则得出患者血清中含有抗-C、e同种抗体以及抗-e、Jk b类同种自身抗体,红细胞上有抗-e、Jk b类同种自身抗体。基因测序分析RHCE基因第5外显子676位出现G>C,其余外显子没有发生突变,推断Rh分型ccEE型;JK基因中第9外显子838 G/A杂合,Jk血型表型Jk(a+b+),选择交叉配血相合的A型ccDEE、Jk(a+b-)红细胞给患者输注,输血效果良好。结论应用吸收放散试验和效价积分法对患者血清进行抗体鉴定,以及血清学结合分子生物学对患者红细胞表型鉴定,可综合分析及区分出抗体的类型,为患者精准输血提供方案。

塔式太阳能吸热器曲面涂层吸收率测试方法研究

吸热器涂层吸收率的准确测量对吸热器性能评估、优化具有重要意义。目前吸热器涂层吸收率的实验研究大多局限于平面金属基材。以塔式太阳能熔盐吸热器圆柱形吸热管为研究对象,提出蓝丁胶法和漫反射盒法2种广泛适用的测量曲面涂层吸收率测试方法。蓝丁胶法器材准备简单,操作复杂;漫反射盒法器材准备复杂,操作简单。2种方法在测量过程中隔绝环境光线干扰,得到各种涂层附着于平板和圆管表面的测量吸收率,通过不同涂层在平板和圆管上的吸收率对应关系建立拟合曲线,从而修正测量数据得到吸热管涂层吸收率,拟合曲线精确性R^(2)≥0.995;不遮光条件下直接测量2.5cm直径吸热管吸收率,最大相对误差为13.39%,使用蓝丁胶法和漫反射盒法后相对误差分别降为0.27%和0.45%,2种方法各点结果相对误差之差小于0.30%,测量过程中涂层吸收率越大,各因素对测量结果影响越小;在蓝丁胶测试方法中,吸热管直径越大,测得的吸收率越小。

模拟降雨条件下南方某城市土壤中铀的迁移转化机制

土壤中放射性核素铀是主要天然辐射贡献者之一,当土壤中铀含量异常时其化学毒性和放射性会对人类健康产生严重威胁。城市是人口高密度区,明确土壤中铀含量水平是城市放射性地质调查重要工作,为城市规划区及潜在规划区提供基础数据支撑。以某城市土壤作为研究对象,通过静态吸附试验和模拟降雨动态淋滤试验方式,对城市放射性地质调查土壤中铀迁移转化机制进行分析研究。结果表明:加Cu离子使土壤铀吸附率下降9.7%;初始铀浓度、吸附时间、粒径大小表明定量土壤中吸附铀酰离子的负点电荷有限;pH为4~6的土壤吸附铀能力最强。SEM分析表明,吸附铀酰后,土壤表面由凹凸不平变为平滑、孔隙度减少及变小。铀在不同pH下的淋洗动力学均符合双常数动力学程,土壤表面对铀的释放表现为一定的微曲线性特征。在pH为4~6自然酸性条件下,当溶液中铀含量大于土壤时,土壤会吸附溶液中铀酰离子;当溶液中铀含量小于土壤时,土壤中铀酰离子易释放到溶液中。该研究为城市放射性地质调查提供了理论依据。

Highly efficient CO_(2) capture using 2-methylimidazole aqueous solution on laboratory and pilot-scale

To date,the primary industrial carbon capture approach is still absorption using aqueous solutions of alkanolamines.Here,to pursue a substitute for the amine-based approach to improve the CO_(2) capture efficiency and decrease the energy cost further,we report a new carbon capture approach using a 2-methylimidazole(mIm)aqueous solution.The properties and sorption behaviors of this approach have been experimentally investigated.The results show that the mIm solution has higher CO_(2) absorption capacity under relatively higher equilibrium pressure(>130 kPa)and lower desorption heat than the methyldiethanolamine solution.91.6%sorption capacity of mIm solution can be recovered at 353.15 K and 80 kPa.The selectivity for CO_(2)/N_(2) and CO_(2)/CH_(4) can reach an exceptional 7609 and 4324,respectively.Furthermore,the pilot-scale tests were also performed,and the results demonstrate that more than 98%of CO_(2) in the feed gas could be removed and cyclic absorption capacity can reach 1 mol·L^(-1).This work indicates that mIm is an excellent alternative to alkanolamines for carbon capture in the industry.

自复位变摩擦阻尼器增强榫卯节点抗震性能研究

研究橡胶碟簧自复位变摩擦阻尼器榫卯节点抗震性能,参照西南地区传统木结构典型做法,制作直榫和台阶透榫节点进行低周反复加载试验,设计增强和未加固试件,对比榫卯节点破坏形态、滞回曲线和骨架曲线。研究结果表明,增设SFD试件拔榫量得以有效降低,榫头断裂、劈裂现象得到显著改善;不同节点滞回曲线均呈Z字形,未加固节点滑移现象更为突出;经SFD加固后的节点滞回曲线更加饱满,耗能能力、承载力和刚度均有显著提升。

基于Overlay Test评价应力吸收层抗反射裂缝性能

为了更好地评价应力吸收层的抗反射裂缝性能,提出采用Overlay Test(OT)试验测定SBS、WTR和WTR/APAO改性沥青应力吸收层在常规条件、浸水和长期老化后的抗反射裂缝性能.研究发现,试验周期数、荷载损失率和总断裂能能够很好地表征应力吸收层的抗反射裂缝性能;第一周期最大荷载和临界断裂能是评价初期开裂的指标.试验发现3种应力吸收层在常规条件下均有良好的抗反射裂缝性能,但是水损坏对WTR/APAO的抗裂性能影响较大,长期老化后WTR和WTR/APAO的抗反射裂缝性能大大降低.3种应力吸收层的OT试验最大荷载-周期数曲线符合幂函数变化规律.

吸湿排汗功能织物研究现状及展望

文章针对影响织物吸湿排汗性能的因素,从润湿芯吸和蒸发排汗两个方面进行分析,介绍吸湿排汗过程中水分传递及分布的测试方法,综述织物吸湿排汗过程的理论模型,包括毛细管芯吸模型和蒸发排汗模型。研究发现,针对织物内部水分芯吸传递的理论研究还比较匮乏。最后,结合纺织品的发展现状与趋势,对吸湿排汗织物未来的研究重点、应用前景和绿色化生产进行展望,为织物性能优化与舒适性面料开发提供参考。

罕见Ael亚型的鉴定及探讨

目的 鉴定与分析1例正反定型不符的ABO血型,为临床疑难血型的鉴定提供参考案例。 方法 采用血型血清学的方法进行ABO、Rh血型、吸收放散试验及基因测序,对1例疑难血型做出准确鉴定。 结果 该患者血液标本经吸收放散试验及分子生物学方法进一步鉴定,确定患者血型为Ael亚型,ISBT命名为 ABO *AEL.05/ABO *O.01.01;经家系调查其次子与先证者拥有同一特征性突变位点,ISBT命名为 ABO *AEL.05/ABO *B.01.01 。 结论 联合应用多种血型血清学试验及分子生物学试验有助于对ABO亚型的鉴定,为临床输血的安全性、科学性、合理性提供保障。

全再生细骨料混凝土的制备及性能试验研究

为提高再生细骨料(regenerate fine aggregates,RFA)的回收使用率,本研究采用一种含砖RFA进行全再生细骨料混凝土(fully recycled fine aggregate concrete,FRFAC)的试验制备.设计吸水率试验拟合公式计算RFA的主要组成及含量;通过设计正交试验研究水料比、减水剂和RFA粒径级配对不同养护天数下FRFAC的强度与热工性能的影响.研究结果表明,该RFA中主要包含废砖、废混凝土和泥块,其含量分别为13.58%、52.98%和33.44%,泥块含量较多,所以在制备前需对RFA进行筛分处理,该RFA平均吸水率较大,所以需采用饱和面干法进行预处理;对FRFAC强度影响最大的是RFA粒径级配,其次是水料比和减水剂,强度随着养护天数呈缓慢上升趋势;FRFAC的导热系数低,通过抗压导热交互分析得到配比最优方案为A3B3C2,制备的FRFAC强度达到25.8 MPa,导热系数为0.4636 W/(m·K),可用于建筑工程中.

浅析原子吸收在地质实验测试中的应用

原子吸收是一种重要的分析技术,因其操作便捷,灵敏度高,能有效提高实验测试数据的精度,减少错误的发生几率,现已被广泛应用于各种地质实验测试中。地质学研究需要准确测量和分析样品中的元素含量和成分,以便于了解地质演变过程、地球变迁历史以及地球内部和表层的化学/物理特征。原子吸收技术在测量样品中特定元素的吸收光谱,并得出准确、敏感和可靠的分析结果方面有着巨大的优势。在目前各类地质实验测试中,原子吸收技术可有效排除各种干扰因子对实验成果精度的影响。本文详细介绍了地质实验测试的作用及其基本流程,剖析了原子吸收法的基本原理及其优势,并对原子吸收法的基本流程及其在地质实验测试中的具体应用展开了分析,以期为地质实验工作者提供借鉴与参考。

Human small intestine is capable of restoring barrier function after short ischemic periods

AIM To assess intestinal barrier function during human intestinal ischemia and reperfusion(IR).METHODS In a human experimental model,6 cm of jejunum was selectively exposed to 30 min of ischemia(I) followed by 30 and 120 min of reperfusion(R). A sham procedure was also performed. Blood and tissue was sampled at all-time points. Functional barrier function was assessed using dual-sugar absorption tests with lactulose(L) and rhamnose(R). Plasma concentrations of citrulline,an amino acid described as marker for enterocyte function were measured as marker of metabolic enterocytes restoration. Damage to the epithelial lining was assessed by immunohistochemistry for tight junctions( TJs),by plasma marker for enterocytes damage(I-FABP) and analyzed by electron microscopy(EM) using lanthanum nitrate as an electrondense marker.RESULTS Plasma L/R ratio's were significantly increased after 30 min of ischemia(30 I) followed by 30 min of reperfusion(30 R) compared to control(0.75 ± 0.10 vs 0.20 ± 0.09,P < 0.05). At 120 min of reperfusion(120 R),ratio's normalized(0.17 ± 0.06) and were not significantly different from control. Plasma levels of I-FABP correlated with plasma L/R ratios measured at the same time points(correlation: 0.467,P < 0.01). TJs staining shows distortion of staining at 30 I. An intact lining of TJs was again observed at 30 I120 R. Electron microscopy analysis revealed disrupted TJs after 30 I with paracellular leakage of lanthanum nitrate,which restored after 30 I120 R. Furthermore,citrulline concentrations closely paralleled the histological perturbations during intestinal IR.CONCLUSION This study directly correlates histological data with intestinal permeability tests,revealing that the human gut has the ability of to withstand short episodes of ischemia,with morphological and functional recovery of the intestinal barrier within 120 min of reperfusion.