残积土动力特性的试验分析研究

本文借助于室内和原位测试方法,以福建泉州花岗岩残积土为例,研究了残积土的基本工程地质特性、微观结构特性、动剪切模量、动应力-应变关系和时间效应,并将其与粘土及砂土进行比较.从大量的共振柱试验和动三轴试验,得到该土饱和及非饱和时的动力参数,非饱和效应,动应力-应变关系以及时间效应的变化规律,并用原位SASW(表面波颇谱分析)法验证了动力参数G_0的可靠性.     

混凝土梁表层嵌贴CFRP板条的抗剪加固性能试验研究

根据7个试件的加载试验．着重研究了表层嵌贴CFRP抗剪加固梁的破坏模式和极限承载力。结果表明。侧面嵌贴CFRP板条可大大提高未配箍筋混凝土梁的抗剪承载力,最大可提高86％;而且比目前工程应用最多的表面粘贴加固方法更有效。同时详细描述和分析了表层嵌贴CFRP抗剪加固混凝土梁的主要破坏模式,即梁侧面FRP-混凝土保护层剥离破坏。     

Jamming and unjamming transition of oil-in-water emulsions under continuous temperature change

To analyze the jamming and unjamming transition of oil-in-water emulsions under continuous temperature change, we simulated an emulsion system whose critical volume fraction was 0.3, which was validated with experimental results under oscillatory shear stress. In addition, we calculated the elastic modulus using the phase lag between strain and stress. Through heating and cooling, the emulsion experienced unjamming and jamming. A phenomenon—which is when the elastic modulus does not reach the expected value at the isothermal system—occurred when the emulsion system was cooled. We determined that this phenomenon was caused by the frequency being faster than the relaxation of the deformed droplets. We justified the relation between the frequency and relaxation by simulating the frequency dependency of the difference between the elastic modulus when cooled and the expected value at the same temperature.     

The mechanical properties of stored red blood cells measured by a convenient microfluidic approach combining with mathematic model

The mechanical properties of red blood cells (RBCs) are critical to the rheological and hemodynamic behavior of blood. Although measurements of the mechanical properties of RBCs have been studied for many years, the existing methods, such as ektacytometry, micropipette aspiration, and microfluidic approaches, still have limitations. Mechanical changes to RBCs during storage play an important role in transfusions, and so need to be evaluated pre-transfusion, which demands a convenient and rapid detection method. We present a microfluidic approach that focuses on the mechanical properties of single cell under physiological shear flow and does not require any high-end equipment, like a high-speed camera. Using this method, the images of stretched RBCs under physical shear can be obtained. The subsequent analysis, combined with mathematic models, gives the deformability distribution, the morphology distribution, the normalized curvature, and the Young''s modulus (E) of the stored RBCs. The deformability index and the morphology distribution show that the deformability of RBCs decreases significantly with storage time. The normalized curvature, which is defined as the curvature of the cell tail during stretching in flow, suggests that the surface charge of the stored RBCs decreases significantly. According to the mathematic model, which derives from the relation between shear stress and the adherent cells'' extension ratio, the Young''s moduli of the stored RBCs are also calculated and show significant increase with storage. Therefore, the present method is capable of representing the mechanical properties and can distinguish the mechanical changes of the RBCs during storage. The advantages of this method are the small sample needed, high-throughput, and easy-use, which make it promising for the quality monitoring of RBCs.     

Optimized frequency-based foundation design for wind turbine towers utilizing soil-structure interaction

This study illustrates design optimization for multiple wind towers located at different villages in Alaska. The towers are supported by two different types of foundations: large mat or deep piles foundations. Initially, a reinforced concrete (RC) mat foundation was proposed. Where soil conditions required it, a pile foundation solution was devised utilizing a 30 in thick RC mat containing an embedded steel grillage of W18 beams and supported by 20-24 in grouted or un-grouted piles. For faster installation and lower construction cost, all-steel foundations were proposed for these remote Alaska sites. The new all-steel design was found to reduce the natural frequencies of the structural system due to softening the foundation. Thus, the tower-foundation system could potentially become near-resonant with the operational frequencies of the wind turbine. Consequently, the likelihood of structural damage or even the collapse is increased.A detailed 3D finite-element model of the tower-foundation-pile system with RC foundation was created using SAP2000. Soil springs were included in the model based on soil properties obtained from the geotechnical investigation. The natural frequency from the model was verified against the tower manufacturer analytical and experimental values. When piles were used, numerous iterations were carried out to eliminate the need for the RC and optimize the design. An optimized design was achieved with enough separation between the natural and operational frequencies. The design successfully avoids damage to the structural system, while eliminating the need for any RC in most cases.     

有腹筋RC梁表层嵌贴CFRP板的抗剪加固试验研究

混凝土结构表层嵌贴碳纤维（CFRP）板或筋,是一种新兴的结构加固方法。本文对2根对比梁和5根表层嵌贴CFRP板条的抗剪加固梁进行了试验研究,考虑了CFRP板间距、CFRP板加固量和箍筋配筋率三个参数对抗剪承载力的影响。研究表明,表层嵌贴CFRP板加固法能有效提高钢筋混凝土有腹筋梁的抗剪承载力。文中还对加固梁的破坏模式作了分析。     

Unnecessary repeated total cholesterol tests in biochemistry laboratory

Introduction

We aimed to determine the number of repeated cholesterol (RC) tests and the ratio of unnecessary-repeated cholesterol (URC) tests among patients admitted to Pamukkale University Hospital (Denizli, Turkey) and provide solutions to avoid URC testing.

Materials and methods

Total cholesterol (T-cholesterol) tests (N = 86,817) between June 2014 and May 2015 were evaluated. The tests performed more than once per patient were determined as RC test (N = 28,811). RC test with an interval shorter than 4 weeks were determined as URC test (N = 3968) according to the shortest retest interval stated in ACC/AHA blood cholesterol guideline. RC testing included internal medicine, surgery and paediatric outpatients and inpatients. Reference change value (RCV) of total cholesterol was calculated.

Results

The 33.1% of the T-cholesterol tests were RC tests (N = 28,811), 13.7% of them were URC tests (N = 3968). Our RCV value was 25%. The percentage change between consecutive tests was less than RCV in 86.1% (N = 3418) of URC tests. URC tests were performed more frequently in patients with desirable total cholesterol value (P < 0.001).

Conclusion

There is a significant part of repeated T-cholesterol tests requested in our hospital. URC test requests can be evaluated by laboratories and the obtained data should be shared with clinicians. Laboratories can calculate RCV for the tests they performed and report this value with the test result. To prevent from URC tests, a warning plug-in can be added to hospital information software in accordance with guidelines to prevent from URC test requests.Key words: unnecessary repeated cholesterol test, cholesterol retest interval, reference change value, laboratory costs, preanalytical phase, test requesting     

天生全球化企业跨国创业导向与国际化绩效——基于网络关系与学习导向动态耦合的视角

本文从网络关系与学习导向动态耦合的视角揭示天生全球化企业独特的跨国创业行为和国际化路径。研究发现,1跨国创业导向是天生全球化企业的国际化基因,网络关系与学习导向都对其有正向影响,阶段性演化机制又使得前者与后两者之间形成了动态三维倒U型相关与三维正相关关系;2网络关系与学习导向的动态耦合共同决定了天生全球化企业形成了创立初期的反应型,成长中期的自主型以及发展后期的维生型三类跨国创业导向,动态网络关系与学习导向的力量对比决定了天生全球化企业跨国创业创新阶段间转换的成功概率及可持续发展能力;3跨国创业导向与天生全球化企业国际化绩效正相关,前者的演化发展伴随后者的动态变化。本文为中小企业创新国际化模式提供了理论支撑与实践启示。     

Mo_3Al_2C力学及电子性质的第一性原理研究

采用基于密度泛函理论的势平面波方法,在0-50 GPa压力作用下,对立方结构Mo3Al2C的力学性质和电子性质进行了研究。计算表明,计算得到的晶格常数与实验值符合的很好,立方结构的Mo3Al2C晶体在0-50 GPa压力下是稳定结构,块体模量,剪切模量,杨氏模量和不可压缩性随着压强的增加而增大而晶格常数和体积逐渐降低。B/G=2.26,表明这个材料是延性材料。电子性质的分析表明,Mo3Al2C表现出金属性,化学键是共价键与离子键的混合。     

碳纤维加固钢筋混凝土柱试验研究与应用

碳纤维加固混凝土柱通过横向约束作用,提高柱的轴心受压承载力,增加柱的延性。利用碳纤维材料作围套加固混凝土轴心抗压柱,具有施工简单、抗腐蚀能力强、约束效果好等优点。     

利用集集地震余震记录分析场地地震动反应

利用1999年台湾地区"921集集大地震"的余震记录,用传统谱比法、线性反演法、S波接收函数法和遗传算法对比分析了车笼埔断层近场区域的场地反应.通过对比4种方法的卓越频率和场地放大因子,发现各种方法能给出较一致的卓越频率,但每种方法的场地反应放大值不完全相同.结果表明,线性反演法与传统谱比法的结果受到参考场自身场地反应的影响;遗传算法作为一种绝对场地反应计算方法其结果是可行的,用遗传算法计算得到的参考场结果对线性反演法结果进行校正,校正后的线性反演法与遗传算法结果非常吻合,也证明了遗传算法结果的可行性,建议推广遗传算法来计算场地反应;接收函数法的结果则同其他3种方法的结果相差较大,考虑到运用强震记录进行H/V方法计算的物理机制仍有争议,建议在实际应用中,慎重考虑应用S波H/V的方法来估计场地放大.最后给出车笼埔断层研究区0.4~20Hz频率范围内S波品质因子值为Qs=69.7f?0.73.     

Current status of the lateral flow immunoassay for the detection of SARS-CoV-2 in nasopharyngeal swabs

Early detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and diagnosis of coronavirus disease 2019 (COVID-19) are priorities during the pandemic. Symptomatic and suspected asymptomatic individuals should be tested for COVID-19 to confirm infection and to be excluded from social interactions. As molecular testing capacity is overloaded during the pandemic, rapid antigen tests, such as lateral flow immunoassays (LFIAs), can be a useful tool as they allow greater test availability and obtain results in a very short time. This short review aims to present the analytical properties of LFIAs in the detection of SARS-CoV-2 in nasopharyngeal swabs. Lateral flow immunoassay is a method that combines thin-layer chromatography and indirect immunochemical sandwich method and allows the detection of a specific SARS-CoV-2 antigen in nasopharyngeal swabs. Swab specimens should be adequately collected and tested as soon as possible. Users should pay attention to quality control and possible interferences. Antigen tests for SARS-CoV-2 show high sensitivity and specificity in cases with high viral loads, and should be used up to five days after the onset of the first symptoms of COVID-19. False positive results may be obtained when screening large populations with a low prevalence of COVID-19 infection, while false negative results may happen due to improper specimen collection or insufficient amount of antigen in the specimen. So as to achieve reliable results, a diagnostic accuracy study of a specific rapid antigen test should be performed.     

Detection of COVID-19 using deep learning techniques and classification methods

Since the patient is not quarantined during the conclusion of the Polymerase Chain Reaction (PCR) test used in the diagnosis of COVID-19, the disease continues to spread. In this study, it was aimed to reduce the duration and amount of transmission of the disease by shortening the diagnosis time of COVID-19 patients with the use of Computed Tomography (CT). In addition, it is aimed to provide a decision support system to radiologists in the diagnosis of COVID-19. In this study, deep features were extracted with deep learning models such as ResNet-50, ResNet-101, AlexNet, Vgg-16, Vgg-19, GoogLeNet, SqueezeNet, Xception on 1345 CT images obtained from the radiography database of Siirt Education and Research Hospital. These deep features are given to classification methods such as Support Vector Machine (SVM), k Nearest Neighbor (kNN), Random Forest (RF), Decision Trees (DT), Naive Bayes (NB), and their performance is evaluated with test images. Accuracy value, F1-score and ROC curve were considered as success criteria. According to the data obtained as a result of the application, the best performance was obtained with ResNet-50 and SVM method. The accuracy was 96.296%, the F1-score was 95.868%, and the AUC value was 0.9821. The deep learning model and classification method examined in this study and found to be high performance can be used as an auxiliary decision support system by preventing unnecessary tests for COVID-19 disease.     

FRP复合材料加固混凝土结构新技术研究进展

近十多年来，国内外对FRP加固(包括改造、修复)混凝土结构这一新技术进行了广泛的试验和理论研究，简要论述了这一新技术的研究进展，着重论述受弯构件加固后的破坏形式和承载力计算方法，包括梁的抗弯加固、梁的抗剪加固和板的抗弯加固等，供实际工程应用参考。     

审计师质量对资本结构的影响——基于联立方程的研究

对于审计师质量与资本结构之间的关系,现有实证研究并不充分,而在理论上,对于这两者之间的关系存在不同的预测。本文利用我国2008-2011年A股上市公司及其主审会计师事务所数据,以行业专长和规模作为审计师质量的替代变量,实证考察我国上市公司基本完成股权分置改革这一背景之下审计师质量对资本结构的影响。结果发现,如果不考虑审计师质量与资本结构之间的相互影响,审计师质量对资本结构没有显著影响;而在考虑这两者之间可能存在相互影响并采用联立方程方法来解决这一内生性问题后,审计师质量对资本结构具有显著的负向影响。进一步研究表明,上述负向关系在国有企业中要比在非国有企业中更为明显。此外,上述负向关系存在于法治环境、信贷环境较好地区,而在法制环境或信贷环境较差的地区,并不显著。     

剪切销断裂过程的仿真研究

对于特殊形状的剪切销,采用传统的剪切试验不能完全满足对其断裂性能的分析要求,本文利用三维造型及有限元分析方法对这种剪切销的断裂过程进行动态仿真模拟,为分析特种剪切销的抗剪强度提供一种理想的方法。     

Dynamic event-triggered control for nonlinear NCSs subject to DoS attacks

In this study, a dynamic event-triggered control problem is addressed for nonlinear networked control systems (NCSs) subject to denial-of-service (DoS) attacks. Assume that data from the plant to the controller is transmitted via a wireless transmission channel under malicious DoS attacks characterized by frequency and duration properties. On the premise of ensuring the stability and minimum inter-event time (MIET) of the systems, dynamic event-triggered mechanisms (DETMs) are proposed for the hybrid dynamic system to withstand a certain degree of DoS attacks. Three event-triggered schemes are designed for the most existing state-based control systems which further enlarge the inter-event times, and the stabilization conditions of hybrid dynamic system are given. Finally, illustrative examples are provided to verify the effectiveness of the presented theoretical results.     

Effect of slippage on the thermocapillary migration of a small droplet

We conduct a numerical investigation and analytical analysis of the effect of slippage on the thermocapillary migration of a small liquid droplet on a horizontal solid surface. The finite element method is employed to solve the Navier-Stokes equations coupled with the energy equation. The effect of the slip behavior on the droplet migration is determined by using the Navier slip condition at the solid-liquid boundary. The results indicate that the dynamic contact angles and the contact angle hysteresis of the droplet are strictly correlated to the slip coefficient. The enhancement of the slip length leads to an increase in the droplet migration velocity due to the enhancement of the net momentum of thermocapillary convection vortices inside the droplet. A larger contact angle leads to an increase in the migration velocity which in turn enlarges the rate of the droplet migration velocity to the slip length. There is good agreement between the analytical and the numerical results when the dynamic contact angle utilizes in the analytical approach obtained from the results of the numerical computation, and the static contact angle is smaller than 50°.     

Microfluidic-based measurement of erythrocyte sedimentation rate for biophysical assessment of blood in an in vivo malaria-infected mouse

This study suggests a new erythrocyte sedimentation rate (ESR) measurement method for the biophysical assessment of blood by using a microfluidic device. For an effective ESR measurement, a disposable syringe filled with blood is turned upside down and aligned at 180° with respect to gravitational direction. When the blood sample is delivered into the microfluidic device from the top position of the syringe, the hematocrit of blood flowing in the microfluidic channel decreases because the red blood cell-depleted region is increased from the top region of the syringe. The variation of hematocrit is evaluated by consecutively capturing images and conducting digital image processing technique for 10 min. The dynamic variation of ESR is quantitatively evaluated using two representative parameters, namely, time constant (λ) and ESR-area (A_ESR). To check the performance of the proposed method, blood samples with various ESR values are prepared by adding different concentrations of dextran solution. λ and A_ESR are quantitatively evaluated by using the proposed method and a conventional method, respectively. The proposed method can be used to measure ESR with superior reliability, compared with the conventional method. The proposed method can also be used to quantify ESR of blood collected from malaria-infected mouse under in vivo condition. To indirectly compare with the results obtained by the proposed method, the viscosity and velocity of the blood are measured using the microfluidic device. As a result, the biophysical properties, including ESR and viscosity of blood, are significantly influenced by the parasitemia level. These experimental demonstrations support the notion that the proposed method is capable of effectively monitoring the biophysical properties of blood.     

一种基于感知特性的鲁棒性语音认证算法

提出了一种基于感知域的鲁棒性语音认证算法,将语音的感知特性与签名算法相结合,在满足内容认证和身份认证的同时,能够有效地抵抗通信噪声微扰.算法基于语音的掩蔽效应和非线性效应等人耳感知特性,着重去除其时频域掩蔽阈值下的冗余信息,进行非线性滤波后提取感知参数,并运用改进的Rainbow算法对这些语音参数进行签名.实验证明,该算法的唯一性和针对通信噪声的鲁棒性都很好,兼有Rainbow签名的安全性保证,可以满足语音通信中的鲁棒性认证要求.