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Recyclable thermosets and thermoset composites with covalent adaptable networks (CANs, or dynamic covalent networks) have attracted considerable attention in recent years due to the combined merits of excellent mechanical and thermal properties, and chemical stabilities of traditional thermosets and recyclable, remoldable, and reprocessable attributes of thermoplastics. In this paper, we present an overview of the current strategies for synthesizing recyclable thermosets based on CANs, which involve recyclability, reprocessability, and possible rehealability. The recent literature examples are categorized based on the underlying controlled-cleavable linkages such as transesterification, DA/retro-DA chemistry, imine bonds, disulfide metathesis, dynamic B-O bonds, hemiaminals/hexahydrotriazines, and acetal linkages. Various degradation and malleability methods and resulting mechanical properties of the recycled thermosets and thermoset composites are presented. The emerging applications of recyclable thermosets and thermoset composites, with emphasis on their usage in adhesives, biomedical materials, wearable devices, coatings, and 3D printing materials, are also illustrated. Finally, a perspective on the challenges and future perspectives is briefly summarized.

In engineering practice, it is difficult to guarantee that the foundation of a beam is homogeneous along the whole length. This paper presents an investigation on buckling and post-buckling behavio...

Introduction: Guillain-Barré syndrome (GBS) is a common autoimmune disease in the peripheral nervous system. This study aimed to elucidate the role of IL-27 gene polymorphisms in elderly people with GBS. Methods: A total of 395 healthy subjects and 422 GBS patients with an average age of 63 years old were included in this study. Peripheral blood samples were collected. The 2 single-nucleotide polymorphisms (SNPs) of IL-27, namely, rs153109 and rs785575, of GBS patients were analyzed using the PCR method and compared with those of the healthy controls. The correlations of IL-27 SNPs with disease severity, disease outcome, level of anti-GM1 antibodies, and Campylobacter jejuni infection were assessed. Serum levels of IL-27 of healthy subjects and GBS patients were analyzed using enzyme-linked immunosorbent assay. Results: No significant differences in the frequencies of rs785575 SNPs between GBS and healthy subjects were observed. In analyzing rs153109 SNPs, the G allele was found to be more prevalent in the GBS patients (p = 0.012). More alleles show GG genotype in GBS patients (p = 0.023). The −964A>G allele has a higher prevalence in severely affected and anti-GM1-Ab-positive GBS patients. GBS patients with the rs153109 SNP showed a poor clinical outcome than those without rs153109 SNP (p = 0.012). GBS patients showed higher serum IL-27 levels than healthy subjects (p < 0.001). The levels of IL-27 were also higher in GBS patients with genotypes of AG and GG, and those with GG genotypes showed the highest IL-27 levels. Conclusion: The rs153109 SNP is more prevalent in GBS patients with the GG and G allele and is associated with severer GBS, poorer clinical outcomes, and higher IL-27 levels.

To reveal the failure mechanism of tunnel structure under active fault movement, based on the pseudostatic elastoplastic finite element method, the failure modes of the tunnel lining are studied under different movement ratios of strike-slip faults and thrust faults with 45° dip angle by using numerical simulation. The results show that the range of significant lining failure section can be determined according to any direction of the coupling fault movement decomposition direction, and the damage effect is determined by the overall movement amount of the coupling fault. The significant damage area of the lining under the action of the coupling fault is the same as the area of deformation, which mainly manifests as tensile failure. Compressive failure occurs in the boundary area between the fracture zone and the hanging wall and foot wall. The plastic strain is the largest in the area where the arch waist and the arch bottom intersect. The development of tunnel lining plastic zone under coupling fault is from arch top and arch bottom to both sides of the arch waist. The development of the plastic zone under active fault is mainly determined by the form of fault with a large ratio. The research results can provide a reference for the design and safety evaluation of tunnel crossing active faults.

Push plate test is a powerful tool to evaluate the interfacial bond performance of China railway track structure type-II slab ballastless track structure (CRTS II SBTS). However, there is still a lack of theoretical explanation of the push plate test. In this paper, a linear proportional distribution method is proposed in terms of a series of analytical formulas to describe the interfacial force-displacement variation of CRTS II SBTS in different damage stages of the horizontal push plate test. The force-displacement relationship established by the linear proportional distribution method agrees well with that observed in full-scale test. The horizontal push plate test is then simulated, in which a bilinear cohesive zone model (CZM) was adopted to simulate the interface within track structure. The parameters of the CZM are calculated based on the force-displacement curves obtained from scale push plate test. Particularly, the normal cohesive parameters are determined based on the scale vertical push plate test instead of the traditional splitting tensile test. The simulation proves that both the maximum affected length in the undamage stage and the maximum damaged length in the damage stage depend rather on the interfacial stiffness and the material parameters of SBTS than the horizontal load. These two lengths given by the simulation are close to those defined by the proposed linear proportional distribution method. This indicates the reliability of the proposed method and the capability of scale push plate test in determining cohesive parameters.

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) undergoes the process of pathological event including lung tissue dysfunction, pulmonary edema, and inflammation in sepsis. Autophagy is a cytoprotective process recognized as one of the major pathways for degradation and recycling of cellular constituents. Autophagy as a protective or maladaptive response was still confused in ALI during sepsis. Acute lung injury was performed by cecal ligation and puncture (CLP). Autophagic inducer rapacymin and inhibitor 3-MA and autophagosomal-lysosome fusion inhibitor bafilomucin (Baf) A1 and chloroquine (CQ) were administrated by intraperitoneal injection at 1 h after CLP operation. Microtubule-associated protein light chain 3 II (LC3II), Beclin 1, Rab7, and lysosome-associated membrane protein type 2 (LAMP2) were detected by western blotting. Seven-day survival rate of septic mice was observed. Histologic scores, lung wet-to-dry (W/D) weight ratio, oxygenation index (PaO2/FiO2), total cells and polymorphonuclear neutrophils (PMN) in bronchial alveolar lavage fluid (BALF) and myeloperoxidase (MPO) activity and cytokine tumor necrosis factor (TNF)-α, high-mobility group box (HMGB)1, interleukin (IL)-6, IL-10, and monocyte chemotactic protein (MCP)1 were measured after sham or ALI operation. ALI induced the increasing expression of autophagy-related protein LC3II, Beclin 1, Rab7, and LAMP2 in CLP operation. Autophagic inducer rapacymin significantly induced the expression of LC3II, Beclin 1, LAMP2, and Rab7 in mice model of CLP, and inhibitor 3-MA reduced expression of LC3II, Beclin 1, LAMP2, and Rab7 expressions in CLP + RAP mice compared to CLP group. Compared with ALI group, Baf and CQ obviously elevated the level of LC3II and Beclin 1, and reduced the LAMP2 and Rab7 expressions in CLP + Baf group and ALI + CQ group. Compared with CLP group, autophagic inducer rapacymin improved the survival rate, histologic scores, lung wet/dry weight ratio, PaO2/FiO2, total cells, and PMNS in BALF and MPO activity and cytokines TNF-α, HMGB1, IL-6, IL-10, and MCP1 in CLP + RAP group, but there were exacerbated above indicators in CLP + 3-MA group, CLP + Baf group, and CLP + CQ group. Autophagy activation participated in the pathophysiologic process of sepsis, and alleviated the cytokine excessive release and lung injury in sepsis.

Increasing heatwave spells associated with global warming profoundly affect the propensity of continuously-welded railway tracks to buckle laterally in a horizontal plane. Train derailments in the presence of buckled tracks endanger the community and are costly to repair. Track buckling is a localization phenomenon, and the amplitude of the buckle increases in the post-buckling range. Because of this, it may not be possible for a train crew at speed to observe a small buckle, or indeed to stop the train if a larger buckle is encountered. There is, therefore, a need to be able to assess the derailment vulnerability as a train passes over a buckled railway track. This paper proposes a finite element modelling of passenger cars and the required speed reduction in circumstances in which railway buckling has occurred. The model of the passenger car is composed of three parts - a carriage, bogies and wheelsets - being connected by springs and dampers. The response of the passenger car is obtained by adopting implicit dynamic analysis, with the analysis being undertaken in the presence of four buckled configurations obtained from non-linear structural analysis. The Weinstock derailment criterion is invoked to describe the vulnerability to derailment, and the derailment index so calculated is shown to increase significantly with the train speed. The effects of the buckle amplitude, the rail size and the ballast resistance on the safe speed are investigated, with the amplitude of the buckle being shown to be the most significant parameter at a particular speed.

In some configuration cases for concrete pavements, such as at the intersection of two road pavements or the connection of a road pavement to a bridge abutment, the pavement can be considered to be semi-infinite with one end adjoining a rigid structure. In addition, continuously reinforced concrete pavements may weaken over time as a result of corrosion, erosion, shrinkage, fatigue cracking or the like, and in these instances the weakened pavement can also be considered as being semi-infinite with a joint. This rotational joint constrains the end of the pavement, which has an effect on the potential upheaval buckling of the pavement when subjected to heatwaves. This paper presents an analytical solution for thermal-induced upheaval buckling of such a semiinfinite continuously reinforced concrete pavement when constrained by a rigid medium with a quantifiable rotational stiffness. The method of minimum total potential energy is invoked to derive the differential equations for the post-buckling response, and the equilibrium equations with variable parameters that govern the behaviour are solved analytically by considering both the deformation of the pavement and the rotational and translational restraints. Parametric investigations are conducted on the buckling response of the pavement when constrained at one end; the parameters considered being the rotational stiffness of the joint, the thickness of the pavement, the properties of the pavement subgrade base and the effective weight of the pavement. It is found that the constraint affects the buckling temperature considerably, and the so-called safe temperature increases with the rotational stiffness of the constraint the end of the pavement.

Heatwaves may cause large axial forces to develop in continuous pavements, with potential buckling taking place when the axial force attains a certain value. With the continual evolution of global warming and prolonged heatwaves, upheaval buckling of continuously reinforced concrete pavements has been a documented problem in highway engineering, as it can have catastrophic consequences. This paper conducts a refined modelling of thermal-induced upheaval buckling of concrete pavements within the framework of general finite element codes. The finite element model is developed by considering the stiffness of the pavement subgrade and the friction between the pavement and its base. Two models of concrete pavements are taken into account: one is a continuous pavement and the other a continuous pavement with a joint. In order to trigger the buckling response, an imperfection of the pavement is incorporated and the configuration of the imperfection is taken from an analytical study. Comparisons between the proposed modelling and the test results, as well as a comparison between the numerical model and the analytical model, are given in the paper. The buckling responses of the pavements are investigated parametrically, with the parameters involved being the pavement thickness, base friction, subgrade modulus, imperfection amplitude, pavement weight and pavement stiffness. Based on the extensive numerical analysis, a prediction model for use in the design of continuously reinforced concrete pavements is proposed.

The blind-hole method is the most widely used approach to experimentally determine the distribution of residual stress. This paper aims to improve test accuracy of welding residual stress and conducts an experimental study on the strain release factors involved when using the blind-hole method for Q235 and Q345, two steels commonly used in building structures. The ranges of strain release factors A and B in the elastic stage, the effects of strain release factors on residual stress calculated values, and the plastic corrected strain release factors are analyzed considering of the effect of plastic deformation around the blind hole on measurement accuracy. Finally, a simplified calculation formula to determine strain release factors is proposed for use with the blind-hole method. Results show that in the elastic stage, strain release factor A for Q235 and Q345 ranges from −0.399 to −0.525 and strain release factor B from −0.791 to −0.960. Changing the strain release factors A and B shows that calculated residual tensile stress varies in relation to a decrease in both factor values. However, there is a increase in calculated residual compressive stress with a decrease in the strain release factor A value, but there is an decrease with a decrease in strain release factor B value. Calculated residual stress applied to elastic strain release factors is compared with that applied to amended plastic strain release factors for Q235 steel. The maximum deviation between calculated residual stress and test stress is reduced from 21.1 to 1.0%, and for Q345 steel from 26.5 to 1.2%. It is thus evident that the plastic correction formula proposed in this paper can be used in calculations when conducting a residual stress test.

Background Accurate intraoperative localization of esophageal lesions is essential for successful surgical resection. We tested whether preoperative endoscopic placement of titanium clips could facilitate intraoperative localization of early-stage esophageal cancer or severe dysplasia. Methods A prospective randomized clinical trial was performed between May 2012 and July 2014. All enrolled patients received preoperative endoscopy and esophageal endoscopic ultrasound, as well as pathological study on the biopsy specimen, to confirm early stage esophageal cancer or severe dysplasia. One day before the surgical operation, patients in the experimental group received the preoperative endoscopic titanium labeling of esophageal lesions. Then, during the surgical operation, palpitation of titanium clips was used to localize the lesions in these patients. In patients in the control group, palpitation of nodules or esophageal wall mucosal thickening, together with the consideration of the results from preoperative endoscopic and ultrasound studies, was applied to estimate the location of the esophageal lesions. Study outcomes included the proportions of patients having successful intraoperative pre-resection lesion localization, post-esophagectomy lesion visualization, negative upper surgical margin, change of surgical approaches, and positive postoperative pathological diagnosis. Results A total of 27 patients were enrolled into the study, with 14 in the experimental group and 13 in the control group. Compared to the patients in the control group, a higher proportion of patients in the experimental group had statistically significant successful intraoperative esophageal lesion localization (100 versus 15.3% in the experimental versus control group). Conclusions Preoperative endoscopic titanium clip placement could facilitate intraoperative localization of early-stage esophageal cancer or severe dysplasia. Trial registration Current study was registered in Chinese Clinical Trial Registry and World Health Organization International Clinical Trials Registry Platform, ChiCTR-INR-17010949 . Registered 22 March 2017, retrospectively registered.

Incorporating oilseed-rape straw in soil is one of the effective methods for enhancing the use efficiency of agricultural resources in the rape-rice rotation system. However, the impacts of oilseed-rape straw incorporation on root growth and dynamic changes in soil are still unclear. In order to provide a deeper understanding of the oilseed rape straw return on rice growth and productivity, the experiment was conducted in the field and in a specially-designed pots system from 2016 to 2017 by means of two straw returning methods and four straw returning amounts. In the early stage of rice growth (0&ndash, 36 days after rice transplanting) the straw returning treatments decreased 1.0&ndash, 8.6 mg/plant in bleeding density and 0.10&ndash, 6.11, 0.06&ndash, 0.31, and 0.52&ndash, 0.84 &mu, mol/(g h) in the activity of glutamine synthetase (GS), glutamic-oxalacetic transaminase (GOT), and glutamic-pyruvic transaminase (GPT), respectively. Oilseed rape straw returned by mulching induced negative impacts on new germinating roots in 0&ndash, 10 cm of soil, while the negative impacts were observed on roots in 10&ndash, 30 cm of soil for straw returned by plowing. In the later stage of rice growth (56&ndash, 75 days after rice transplanting), oilseed rape straw returning produced some positive impacts on rice roots, which enhanced the yield of rice. Conclusively, our findings suggested that dynamic root growth and the activity of root enzymes are two major factors behind the slow reviving of rice after transplanting in the straw returning field. Plowing is a more appropriate method of straw returning than mulching in the rape-rice rotation system in the Sichuan basin area, with a straw incorporation rate of 3.0 t/hm2.

Multi-span suspension bridges show special structural characteristics compared with conventional suspension bridges. The mid-pylon is vulnerable to fatigue failure due to the effects of wind loads and traffic loads. In this study, based on the engineering context of the Taizhou Yangtze River Bridge, some investigations were conducted on the structural behaviour of this multi-span suspension bridge. Fatigue strength tests of two critical details on the steel mid-pylon were carried out. The two details were the butt weld of two segments near the longitudinal full penetration weld and the longitudinal full penetration weld near the diaphragm. Crack propagation was observed in the tests, and it was found that the initial crack propagation directions of the two details were different. S-N curves for these two details are not included in relevant bridge design codes, and in this study, fatigue strength values of the two details are proposed based on their fatigue tests. It is suggested that the fatigue strength value corresponding to two million-cycles for the detail of the butt weld of two segments near the longitudinal full penetration weld is 85.6 MPa, and the fatigue strength value corresponding to two million-cycle for the detail of the longitudinal full penetration weld near the diaphragm is 101.5 MPa.

Steel-plate composite (SC) panel consists of two steel plates, a core concrete, and various types of mechanical connectors. The SC panel demonstrates the high bearing capacity and energy dissipation capacity against impact loading. This paper put forwards an improved two-degree-of-freedom (TDOF) mass–spring–damper model to evaluate the impact response of the SC panel. The derivations and verifications are discussed and results show that the model gives satisfactory predictions on both failure modes and impact responses, including impact force, projectile displacement, and panel deflection time histories.

A wind measurement Doppler Lidar system was developed, in which injection seeded laser was used to generate narrow linewidth laser pulse. Frequency stabilization was achieved through absorption of iodine molecules. Commands that control the instrumental system were based on the PID algorithm and coded using VB language. The frequency of the seed laser was locked to iodine molecular absorption line 1109 which is close to the upper edge of the absorption range,with long-time (>4 h) frequency-locking accuracy being ≤0.5 MHz and long-time frequency stability being 3.55×10 −9 . Design the continuous light velocity measuring system, which concluded the cure about doppler frequency shift and actual speed of chopped wave plate, the velocity error is less than 0.4 m/s. The experiment showed that the stabilized frequency of the seed laser was different from the transmission frequency of the Lidar. And such frequency deviation is known as Chirp of the laser pulse. The real-time measured frequency difference of the continuous and pulsed lights was about 10 MHz, long-time stability deviation was around 5 MHz. When the temporal and spatial resolutions were respectively set to 100 s and 96 m, the wind velocity measurement error of the horizontal wind field at the attitude of 15–35 km was within ±5 m/s, the results showed that the wind measurement Doppler Lidar implemented in Yanqing, Beijing was capable of continuously detecting in the middle and low atmospheric wind field at nighttime. With further development of this technique, system measurement error could be lowered, and long-run routine observations are promising.

Beijing Na–K lidar has been started running in 2010. This lidar has two laser beams: one dye laser emits a 589-nm laser beam for Na layer detection; the other dye laser emits a 770-nm laser beam for K layer detection. Under similar conditions, the echo signal of K layer is only about 2 orders of magnitude smaller than that of Na layer. This lidar has a sufficient Signal Noise Ratio (SNR). The structure and details of potassium layer can be effectively distinguished from a single original echo. Several examples of co-observation of density of Na and K layer showed some different results with previous studies. This lidar not only can supplement the lack of Na and K layer observation at this latitude region, but also provide evidence for the atmospheric sciences and space environment monitoring.

Railway tracks are vulnerable to buckling when subjected to temperature increases, as occurs frequently during heatwaves. This paper presents an investigation of the lateral buckling and postbuckling response of railway tracks under thermal loading that includes the restraining effect of the ballast in the longitudinal and lateral directions. The principle of stationary total potential is used to develop the differential equations of equilibrium, as well as the bifurcation buckling from this equilibrium, and these equations are shown to be highly non-linear. The buckling analysis shows that first-order symmetric and antisymmetric modes may govern the buckling, and that for very long members the two buckling loads are the same. The highly non-linear equations for the postbuckling response are solved by making recourse to a shooting technique, and it is shown that following the bifurcation buckling under displacement control the response is initially unstable, followed by a stable branch of the postbuckling equilibrium response. Under thermal loading, which occurs in practice, the response is one of snap-through buckling to the remote stable path, and the solution is shown to capture the localisation of the buckling modes that is observed in practice. The effects of the lateral and longitudinal ballast resistance are quantified, and it is shown that the lateral resistance is predominant when compared with the longitudinal resistance. The influence of lateral track imperfections is also studied, which is shown to have considerable effect on the critical temperature.

This paper reports that the sodium–potassium (Na–K) lidar was completed in November 2016 at Sao Jose Dos Compose, Brazil (23°S, 45°W), by the joint effort of the National Space Science Center, Chinese Academy of Sciences (NSSC) and Instituto Nacional de Pesquisas Espaciais (INPE). This system realized the Na and K metal layers simultaneously observe in Brazil, and this is the first instance of K layer detection in South America. Some of the key parameters and technologies have been optimized based on the Na and K layer dual-wave lidar in Beijing Yanqing station, such as improve technical parameters for receiving telescope, the narrow linewidth, efficient laser frequency doubling, the wavelength automatic locking techniques. By adopting these technologies, the output were 589 nm and 770 nm lasers, with high emission powers of 75 mJ and 83 mJ, respectively, and backscattered signals of Na and K layers with high signal quality were obtained. Observation data showed that the original echo photon count of the Na layer was approximately 42,486 (time resolution: 200 s, spatial resolution: 96 m) and the number of noise photons was 286 in a single data acquisition. The signal-to-noise ratio was up to 205:1. At the same spatiotemporal resolution, the original echo photon count of the K layer was approximately 1633, the noise photons were 38, and the signal-to-noise ratio was up to 40:1. The initial photocounts received has demonstrated that the Brazil K lidar has produced high quality signal with signal-to-noise level required by intended science studies. Moreover, the simultaneous phenomena of sporadic Na (Nas) and sporadic K (Ks), and the highly concentrated layers of atomic K have been observed, the K density in these narrow layers exceeds 1019 cm−3.

Equipped with a 1-meter Cassegrain telescope with 6.2 meter focal length and an electronically gated Intensified Charge-Coupled Device (ICCD), a multilayer Na imager is designed and developed at Wuhan in China. This novel instrument has successfully achieved the first preliminary 3-D image of the mesospheric Sodium (Na) layer when running alongside a Na lidar. The vertical Na layer profile is measured by the lidar, while the horizontal structure of the layer at different altitudes is measured by the ICCD imaging with a horizontal resolution of ~3.7 urad. In this experiment, controlled by the delay and width of the ICCD gating signal, the images of the layer are taken with three-second temporal resolution for every 5 km. The results show highly variable structures in both the vertical and horizontal directions within the Na layer. Horizontal images of the Na layer at different altitudes near both the permanent layer (80–100 km) and a sporadic Na layer at 117.5 km are obtained simultaneously for the first time. The Na number density profiles measured by the lidar and those derived from this imaging technique show excellent agreement, demonstrating the success of this observational technique and the first 3-D imaging of the mesospheric Na layer.

A dual-wavelength tunable lidar system that simultaneously detects the Ca and C a + layers has been established in Yanqing Station (40.41°N, 116.01°E). The lidar system implements a pulsed Nd:YAG laser that simultaneously pumps two dye lasers, which reduces the hardware configuration of the lidar system. The two dye lasers use infrared laser dyes with high conversion efficiency suitable for long-term observation. The resonance wavelengths of Ca and C a + are generated by frequency doubling of the two infrared laser beams. We compared the dual-wavelength tunable lidar system to previous dye-based systems and performed experiments to determine resonance frequencies to within 0.4 pm and to test the dual optical fiber receiving system and found it does not cause cross talk. Three nights of preliminary simultaneous observations of Ca and C a + layers are reported; the diversity of these observations begs for more systematic observations and challenging interpretations in terms of Ca processes in the ionosphere and illustrates the effectiveness of this system for aeronomy and space physics studies.

To save the computational efforts of Monte Carlo simulation together with nonlinear finite element method, the analysis framework combining the response surface method and Monte Carlo simulation is usually adopted to investigate the stochastic nonlinear behavior of structures. It is found that the traditional response surface method could not describe stochastic behavior of cracked concrete beams. In order to overcome the discontinuity caused by cracking nonlinearity, a scheme by introducing a piecewise response surface is proposed in this paper. This scheme is evaluated by the stochastic analysis of several concrete beams. The comparison between the proposed method and some traditional methods, including Monte Carlo simulation and Monte Carlo simulation with traditional response surface, shows that the proposed method could well depict the stochastic behavior of concrete beams. Finally, the probability density evolution of concrete beams from short-term deflection to a long-term deflection is analyzed.

In the non-linear in-plane elastic buckling and postbuckling analyses of shallow parabolic arches, to overcome the difficulty in deriving an accurate expression for the non-linear normal strain, an approximation assumption that the derivative of the vertical coordinate with respect to the horizontal coordinate satisfies ( d y / d z ) 1 ≪ 1 has been adopted in many investigations. The merit of the assumption is that it leads to the same differential equations of equilibrium and the same solutions as those for shallow circular arches. However, the accuracy of the assumption and the limitation of the analytical solutions have not been examined and because of the approximation, the analytical solutions may lead to significant errors for the buckling loads of shallow parabolic arches in some cases. This paper investigates the effects of the approximation assumption on the accuracy of in-plane buckling and postbuckling analyses of pin-ended and fixed shallow parabolic arches by comparing the analytical solutions with their finite element counterparts. It is found that the analytical solutions based on the assumption have some limitations because the assumption holds approximately only for extremely shallow parabolic arches, but is not valid for most shallow parabolic arches. The analytical solutions for the buckling loads based on the assumption are larger than the corresponding finite element results for parabolic arches with a rise-to-span ratio greater than 0.08, the error of the analytical solution increases with an increase of the rise-to-span ratio of the arch, and the sources for the errors are identified and discussed. Hence, caution should be exercised when using the analytical solutions to predict the buckling load of shallow parabolic arches, particularly of those with a rise-to-span ratio greater than 0.08.

Structural columns in engineering practice may weaken over time as a result of corrosion, erosion, impact, fatigue cracking or similar effects that reduce their effective cross-section. The effect of the degradation of the cross-section may then lead to premature flexural buckling. This paper presents a solution for the buckling and post-buckling behaviours of such weakened columns under thermal loading. The method of minimum total potential is employed to derive the differential equations for the buckling, as well as those for the post-buckling response, and the boundary value equations with variable coefficients that govern the behaviour are solved using a shooting procedure. The buckling and post-buckling responses of weakened columns are investigated parametrically, and it is found that the weakening of the column may affect the buckling temperature significantly. Comparisons between the solutions of the problem that account for, and do not account for, the axial deformation are also given, and the results indicate that the effects of axial deformation need to be considered under thermal loading. A Rayleigh–Ritz solution for weakened columns is also presented, and it is found that the proposed simplified formulation can predict the buckling and post-buckling responses of weakened columns under thermal loading quite accurately.

This paper aims at evaluating rural household development capability in the procedure of ecological migration in Ningxia with fuzzy mathematics method. To achieve this goal, an indicator system of rural household development capability, which consists of 3 first-class indicators, 21 second-class indicators and 57 third-class indicators, is established. The data applied in this research are acquired from a field investigation to Liupanshan poverty-ridden areas in Ningxia. According to the results, rural household development capability of resettlement areas has increased compared with that of montanic areas, as is reflected in the three first-class indicators, self development capability, self development awareness and public atmosphere. However, at the same time, a few second- and third-class indicators have decreased owing to migration, such as per capita net income, guanxi network and money-raising ability, etc. This offers an overall view of the changes in peasants’ life, and accordingly a few suggestions on future implementation of the migration policy.

Field investigations reveal that railway tracks, pipelines, and pavements are prone to buckling locally as a result of the axial compressive forces caused by thermal loading. These types of...

Long slender elastic structures, such as railroad tracks, pipelines, and pavements, may experience buckling owing to axial compressive forces developed in them as a result of thermal or oth...

A solid-state sodium (Na) Doppler lidar developed at YanQing Station, Beijing, China (40°N, 116°E) aiming to simultaneous wind and temperature measurement of mesopause region was reported. The 589 nm pulse laser was produced by two injection seeded 1064 nm and 1319 nm Nd:YAG pulse lasers using the sum-frequency generation (SFG) technique. A fiber amplifier is implemented to boost the seed power at 1064 nm, enabling a robust, all-fiber-coupled design for seeding laser unit, absolute laser frequency locking, and cyclic three-frequency switching necessary for simultaneous temperature and wind measurements. The all-fiber-coupled injection seeding configuration together with the solid-state Nd:YAG lasers make the Na Doppler lidar more compact and greatly reduce the system maintenance, which is conducive to transportable and unattended operation. A preliminary observational result obtained with this solid-state sodium Doppler lidar was also reported in this paper.

Due to the severe interference from strong solar background light on the received signal, daytime ground-based lidar observation of the sodium (Na) layer is challenging. In this paper, a Na lidar permitting full-diurnal-cycle observation of the metal Na layer over Beijing, China (40.5°N, 116°E) was reported. In order to suppress the skylight background during daytime effectively with less signal losses, a dual-channel Faraday filtering unit was implemented in the lidar receiver. Based on the diurnal Na lidar system, a good number of continuous observational results that lasted more than 120 h with good signal-to-noise ratio were obtained, demonstrating its reliability. Considerable variations within the Na layer during the day were revealed, especially on the layer top and bottom side. In particular, strong sporadic Na layer (Nas) events that occurred during the daytime of 3 consecutive days were also captured with complete evolution process. These observational results showed the advantages of the diurnal Na lidar for investigating the metal layer photochemistry and dynamics in the mesosphere and lower thermosphere region. Na layer observations over the whole diurnal cycle not only benefit the improvements of current theoretical models, but also can allow for a specialized analysis of Nas that occur in the daytime and provide valuable observational support for investigating the rapid production and disappearance mechanisms of Na atoms.

Recently, asphalt supporting layer (ASL) has been adopted as a novel technology to waterproof subgrade and increase stability of slab track in China. Asphalt concrete is a typical thermal sensitive material and its mechanical properties are very susceptible to temperature conditions, which makes it very brittle at low temperature and easy to suffer from deformation at high temperature. Therefore, it is essential to investigate the temperature features of ASL in slab track during its service life. In this paper, the temperature distribution within ASL was studied by combining field recorded data and numerical simulation, and the effects of meteorological factors including air temperature, solar radiation, and wind speed were numerically studied with emphasis. The results show that the temperature within ASL distributed non-uniformly along the cross section of ASL, and the temperature of the area directly underneath the track slab was much more stable than other areas exposed to the air. The variation of meteorological factors including air temperatures, solar radiation and wind speed has significant effects on the temperature of ASL, but it takes hours for the change of meteorological factors to be seen within ASL. There is a linear relation between the change of ASL temperature and the variation of air temperature and solar radiation incident, but the influence of wind speed decreases with the increasing of wind speed. Meanwhile, the temperature of ASL is more susceptible to solar radiation and wind speed in summer, and it is more easily affected by air temperature in summer.

In regions of high shear forces in composite bridges, headed stud shear connectors need to be arranged with a small spacing in order to satisfy the design requirement of resisting the high interface shear force present at this location. Despite this, studies related to groups of headed studs are somewhat rare. This paper presents an investigation of the static behaviour of grouped stud shear connectors in high-strength concrete. Descriptions are given of five push-out test specimens with different arrangements of the studs that were fabricated and tested, and the failure modes, load-slip response, ultimate load capacities and related slip values that were obtained are reported. It is found that the load-slip equation given by some researchers based on a single stud shear connector in normal strength concrete do not apply to grouped stud shear connectors in high-strength concrete, and an algebraic load-slip expression is proposed based on the test results. Comparisons between the test results and the formulae provided by some national codes show that the equations for the ultimate capacity provided in these codes are conservative when used for connectors in high-strength concrete. A reduction coefficient is proposed to take into account the effect of the studs being in a group.

During the last decades, asphalt concrete has been introduced in both ballast and ballastless track (including but not limited to slab track) systems. The use of asphalt concrete provides better damping and waterproofing performance. For this reason, a supporting layer of asphalt concrete (ASL) was introduced to the latest Chinese slab track system. In this paper, an in-depth study of the dynamic behavior of ASL was presented using modelling and in-situ measurement approaches. In the FE model, the train load was simplified to be a time series of concentrated load on rail nodes, and asphalt concrete was modeled as viscoelastic material by Prony series. The FE model was validated against in-situ measurement on a test section, in which a monitoring system was setup during construction. A series of transient analysis were conducted to obtain the dynamic responses of ASL under moving train load. The parametric effects of thickness of ASL was also studied with respect to the dynamic responses of superstructure and substructure, as well as the stability and durability of ASL. The results showed that, under moving bogie load, the reach of the dynamic responses in ASL is about 7.5 m in the longitudinal direction, and the maximum values occur at the position beneath the rails. A thicker ASL is more favorable to ride comfort and structural stability of high-speed railway track system. However, considering the economic and construction factors, an optimal thickness range of 7–10 cm is suggested for ASL in CRTS III slab track.

In the doppler wind lidar, usually every 4MHz frequency error will produce wind error of 1m/s of 532nm laser. In the Doppler lidar system, frequency stabilization was achieved through absorption of iodine molecules. Commands that control the instrumental system were based on the PID algorithm and coded using VB language. The frequency of the seed laser was locked to iodine molecular absorption line 1109 which is close to the upper edge of the absorption range, with long-time (>4h) frequency-locking accuracy being≤0.5MHz and long-time frequency stability being 10- 9 . The experimental result indicated that the seed frequency and the pulse laser frequency have a deviation, which effect is called the laser chirp characteristics. Finally chirp test system was constructed and tested the frequency offset in time. And such frequency deviation is known as Chirp of the laser pulse. The real-time measured frequency difference of the continuous and pulsed lights was about 10MHz, long-time stability deviation was around 5MHz. After experimental testing technology mature, which can monitoring the signal at long-term with corrected the wind speed.

A reliable and robust shear connection is required in the cast in situ portion of a segmental composite bridge girder to carry the shear force between the steel and concrete. When the shear connectors are arranged with close spacing in order to satisfy design requirements, group effects will have a significant influence on the structural behavior of the shear connection. This paper presents an investigation of the static behavior of group-arranged stud–bolt hybrid shear connection in long-span segmental bridges, with the bolt shear connectors as the threaded outstands of the high-strength bolts used in the splice connections needed in segmental construction. Seven specimens with different arrangements of the studs and high-strength bolts were fabricated and tested. The failure modes, load-slip relationships, and shear strength were obtained and discussed. The results showed that the bolts could increase the shear strength of the connection and that the embedded length of the bolts had a marked eff...

Perfobond rib shear connectors are used widely in bridge engineering, and expressions for their shear capacity can be found in various codes and standards. Empirical expressions available for the strength of perfobond rib shear connectors have been obtained mostly by the numerical regression analysis of push-out test results. Because of discrepancies in both specimen dimensions and the test procedures, the various test results do not agree with each other, and the empirical strength predictions so derived are quite different. To resolve this discrepancy, the authors investigated the modes of failure of perfobond shear connections using a novel push-out test procedure. The mechanisms for the resistance to load of perfobond rib shear connectors were analyzed, and the effects of the concrete and transverse reinforcement on the shear resistance were investigated. An empirical expression for the shear strength of perfobond rib shear connectors with transverse reinforcement is proposed here. The calcula...

To study the effect of Aidi Injection (艾迪注射液,ADI) applied in the bronchial artery, applied in the bronchial artery infused (BAI) neo-adjuvant chemotherapy for stage III A non-small cell lung cancer (NSCLC) before surgical operation.The 60 patients with NSCLC stage III A underwent two courses BAI chemotherapy before tumor incision were assigned to two groups, the treatment and the control groups, using a random number table, 30 in each group. ADI (100 mL) was given to the patients in the treatment group by adding into 500 mL of 5% glucose injection for intravenous dripping once daily, starting from 3 days before each course of chemotherapy, and it lasted for 14 successive days, so a total of 28 days of administration was completed. The therapeutic effectiveness and the adverse reaction that occurred were observed, and the levels of T-lymphocyte subsets, natural killer cell activity, and interleukin-2 in peripheral blood were measured before and after the treatment.The effective rate in the treatment group was higher than that in the control group (70.0% vs. 56.7%, P0.05). Moreover, as compared with the control group, the adverse reaction that occurred in the treatment group was less and mild, especially in terms of bone marrow suppression and liver function damage (P0.05). Cellular immune function was suppressed in NSCLC patients, but after treatment, it ameliorated significantly in the treatment group, showing significant difference as compared with that in the control group (P0.05).ADI was an ideal auxiliary drug for the patients in stage III A NSCLC received BAI neo-chemotherapy before surgical operation; it could enhance the effectiveness of chemotherapy, ameliorate the adverse reaction and elevate patients' cellular immune function; therefore, it is worthy for spreading in clinical practice.

The application of prestress is a very effective way to prevent the cracking of the concrete slab in the negative-moment region of continuous composite girders, and using a prefabricated prestressed-concrete slab in this region is an easier option than posttensioning. To elucidate the structural response of a continuous composite box girder with a prefabricated prestressed-concrete slab, two large, 18-m-long specimens were fabricated and tested under short-term loading, and the results are reported in this paper. One, a control specimen, was a conventional composite girder with its concrete slab cast in situ, whereas the other was a composite box girder with a prefabricated prestressed-concrete slab in the negative-moment region. The relative slip between the steel girder and the concrete slab; the load-deflection response; the distribution of strain in the steel girder, reinforcement, and concrete slab; as well as the crack widths in the concrete slab were measured during the tests. The paper sho...

For high power-aperture lidar sounding of wide atmospheric dynamic ranges, as in middle-upper atmospheric probing, photomultiplier tubes' (PMT) pulse pile-up effects and signal-induced noise (SIN) complicates the extraction of information from lidar return signal, especially from metal layers' fluorescence signal. Pursuit for sophisticated description of metal layers' characteristics at far range (80~130km) with one PMT of high quantum efficiency (QE) and good SNR, contradicts the requirements for signals of wide linear dynamic range (i.e. from approximate 10(2) to 10(8) counts/s). In this article, Substantial improvements on experimental simulation of Lidar signals affected by PMT are reported to evaluate the PMTs' distortions in our High Power-Aperture Sodium LIDAR system. A new method for pile-up calibration is proposed by taking into account PMT and High Speed Data Acquisition Card as an Integrated Black-Box, as well as a new experimental method for identifying and removing SIN from the raw Lidar signals. Contradiction between the limited linear dynamic range of raw signal (55~80km) and requirements for wider acceptable linearity has been effectively solved, without complicating the current lidar system. Validity of these methods was demonstrated by applying calibrated data to retrieve atmospheric parameters (i.e. atmospheric density, temperature and sodium absolutely number density), in comparison with measurements of TIMED satellite and atmosphere model. Good agreements are obtained between results derived from calibrated signal and reference measurements where differences of atmosphere density, temperature are less than 5% in the stratosphere and less than 10K from 30km to mesosphere, respectively. Additionally, approximate 30% changes are shown in sodium concentration at its peak value. By means of the proposed methods to revert the true signal independent of detectors, authors approach a new balance between maintaining the linearity of adequate signal (20-110km) and guaranteeing good SNR (i.e. 10(4):1 around 90km) without debasing QE, in one single detecting channel. For the first time, PMT in photon-counting mode is independently applied to subtract reliable information of atmospheric parameters with wide acceptable linearity over an altitude range from stratosphere up to lower thermosphere (20-110km).

Low temperature property of asphalt mixture has been one of the worldwide focuses in pavement research. This paper focuses on property of stone matrix asphalt (SMA), mastic asphalt (MA) with that of epoxy asphalt mixture, which are currently widely used in steel bridge deck pavement. During calculation, a three-parameter solid model is employed with its corresponding parameters obtained by nonlinearly regressing the data from bending creep test. Additionally, based on the principle of time-temperature equivalence and linear superposition, thermal stress equation is achieved, through which thermal stress of the three kinds of mixture are calculated with an assumption of constant cooling rate. By comparing the calculation results with that of thermal stress restrained specimen tensile test (TSRST), this equation is found to be adequate to compute the thermal stress at low temperature. Also in this study, the thermal stress is calculated concerning full bonding conditions between steel deck and the mixture. It shows that when the thermal expansion coefficient of the steel deck is ignored, thermal stress will be exaggerated to a great degree. Also, it is found that epoxy asphalt mixture performs the best in terms of low temperature performance.