Abstract: Odor pollution from typical sources has drawn enormous attention because of its strong irritation potential and wideranging and harmful effects to nearby residents. Substantial studies on evaluation methods and characterization of such odor pollution have been conducted all over the world. Advancements in sampling and analysis, prediction methods, and the characterization of odor pollution have taken place in recent years. In this study, specific literature was reviewed on evaluation and prediction methods, characterization, and control strategies for odor pollution from typical waste disposal facilities.
Abstract: Pole figures measured using X-ray diffractometry were used to analyze the orientation of crystalline hydroxylapatite (HAP) in the scales and fins of seawater Lateolabrax japonicus. An orientation distribution function (ODF) was calculated based on the pole figures of the lattice planes (002),(130), and (211) of HAP in the scales and those of (031),(120), and (132) in the fins. The pole figures indicate that the c-axis of HAP prefers three primary orientations in the scales and five primary orientations in the fins. In the scales, the preferred orientations of the HAP c-axis are parallel to the normal line of the scale face and intersect the normal line at about 39° and 63°. In the fins, the HAP c-axis intersects the normal line of the cross-section at 3°, 9°, 17°, 24°, and 36°. However, the calculated ODFs show that the preferred orientations of the HAP c-axes are nearly parallel to the face of the scales and perpendicular to the cross-section of the fins. As the pole figure only reflects a two-dimensional projection of the crystalline orientations, the preferred orientations determined by the pole figures are not very accurate. Conversely, three-dimensional ODF is more suitable for analyzing the preferred orientation of biominerals than the two-dimensional projection. The tendency of the c-axis to be parallel to the collagen fibers is controlled by organic matter and provides a good mechanical performance in hard tissue.
Abstract: Gypsum rock is strongly corrosive and expansive, which can cause significant deterioration in the lining structure and the strength over the life sysle of a geologic tunnel. It would seriously affect the reliability of the tunnel lining structure reliability and negatively impact complex structural rules. In this reported study, the expansion failure and corrosion failure modes of the lining structure were established according to the influence of the expansive character and the corrosivity of the gypsum wall rock on the tunnel lining structure. Based on the combined effects of swelling and the corrosivity of gypsum on the tunnel lining structure, a comprehensive failure mode for the gypsum rock tunnel lining structure was established. Based on the structural functions, a derived reliability index formula for the tunnel lining structure based on the swelling and erosion of surrounding rock was established. A reliability analysis model of the gypsum in three failure modes was instituted. Based on the failure mode of the surrounding gypsum rock, the time-dependent reliability model of Lirang tunnel was analyzed, and a rule for the reliability index in a life span over a period of 100 years was obtained. According to the calculated results, the corrosion resistance, anti-swelling and supporting structure design parameters of the tunnel lining structure of gypsum rock could be optimized, and rational maintenance and repair of the gypsum rock tunnel life-cycle was provided. The research results can be applied to reliability research of tunnel lining structures.
Abstract: To investigate the microscopic damage characteristics of rock materials under cyclic dynamic disturbance, granite was chosen as the research object, and the split Hopkinson pressure bar (SHPB) was used to outperform the cyclic impact test. Besides, with the nuclear magnetic resonance (NMR) technique, the porosity, crosswise relaxation time T2 distribution and magnetic resonance image (MRI) of the rock sample were obtained. The results show that within the range of the rock's elastic limit, the porosity reduces after the dynamic disturbance. The initial and final transverse relaxation time T2 shortens, which indicates the process of cyclic disturbance causes the formation of small pores, where the size and number of large pores decrease. The decrease of porosity does not mean that the number of all kinds of pores decreases; on the contrary, the number of small pores increases, and the decreased number of large pores is the root cause which leads to the decrease of porosity after dynamic disturbance.
Abstract: Preparation of red-mud based paste-like backfill material using red mud, coal gangue, and other industrial solid wastes was accounted. In order to understand the hydration characteristics of red-mud based paste-like backfill material, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric-differential scanning calorimetry, and scanning electron microscope-energydispersive X-ray spectroscopy techniques were used to investigate the hydration products of the hardened paste, which was formed after hydration of raw materials. The results show that the most optimized proportion is the number E03 experiment, in which the mass ratio of cementing material, red mud, coal gangue, and additive agent is 1:16:5:11, the solid mass fraction is 70%, and the uniaxial compressive strength after 28 days is 5.49 MPa. The hydration products of red-mud based paste-like backfill material are mainly gismondine (CaAl2 Si2O8·4H2O) and ettringite (AFt). As the hydration reaction proceeds, the quantity of hydration products increases significantly. Needle-shaped ettringite forms during the early hydration period and gradually transforms into rod-shaped ettringite; this transformation is helpful in the strength development of the red-mud based paste-like backfill material.
Abstract: Three-dimensional (3D) graphene foam (GF) was synthesized by chemical vapor deposition (CVD). Following this, ZnO nanowire arrays (ZnO NWAs) were grown on the 3D GF by hydrothermal synthesis. Finally, carbon (C) was deposited on the surface of ZnO NWAs by CVD to obtain a C/ZnO NWAs/GF hybrid. This composite was used to detect the presence of folic acid. The experimental results show that the GF inherits the 3D macroporous structure of nickel foam and that the ZnO NWAs are uniformly and vertically grown on the 3D GF. The length and diameter of the ZnO nanowires are~50 nm and 2 μm, respectively. Carbon is deposited on the surface of ZnO NWAs, and the C/ZnO NWAs/GF is used as a working electrode to detect folic acid (FA) using an electrochemical method. The experimental results show that the sensitivity of the electrode for FA is 0.13 μA·μmol-1·L and it has good selectivity for detecting FA in the presence of uric acid. The electrode also has excellent reproducibility and stability.
Abstract: A thermodynamic model for gas-solid reduction reactions of iron oxides was established based on the minimized Gibbs free energy principle. On the basis of the model calculation results, the equilibrium diagram for the gas-solid reduction reactions of iron oxides was graphed; the equilibrium results are in good agreement with the reported experimental data. Comparison with the data from common metallurgical books and thermodynamic databases indicates big differences in thermodynamic data from different references. Thermodynamic equilibrium was investigated for the stepwise reduction sequence of iron oxides. The thermodynamic equilibrium was calculated for iron oxide reduction using CO-H2 mixtures as a reducing agent. According to the calculation results, the formula for the gas utilization ratio η總 in the equilibrium state was deduced, and the three-dimensional equilibrium diagram of iron oxide reduction using CO-H2 mixtures was graphed. As compared with the reported experimental data indicates the correctness of calculation results.
Abstract: This investigation sought to determine the effect of solidification & heat transfer behavior and AlN precipitation on the quality of a Q420C billet and rolled product during the process of high straightening strain. To accomplish this, the paper employed a ProCAST simulation and a nail-shooting experiment to calculate the surface and corner temperature of the billet and the thickness of shell, and a formula for the thickness of solidified shell was proposed. The slab has a good plasticity in the temperature range of 1008-1364℃ based on the results of the Gleeble experiment. The thermodynamics and kinetics of AlN precipitation show that the billet should be straightened avoid the "window" of AlN precipitation and before steel rolling, the billet temperature should be controlled to between 1160-1200℃, and the final rolling temperature should be above 850℃. This reduces AlN precipitation in the austenite grain boundary. After the test, the Q420C steel was successfully produced. The average qualified rate of the rolled products reached 90% and the comprehensive performance index met the needed requirements.
Abstract: Vanadium-titanium magnetite is one of the important raw materials for iron making in a blast furnace. Ca3TiFe2O8, which is a mineral of vanadium-titanium sinter, was discovered to form during the process; however, its formation mechanism is not clear. In this work, an X-ray diffraction analysis, an elemental spectroscopy, and a TG-DSC were employed to investigate the formation mechanism of Ca3TiFe2O8 and the formation law at different temperatures and at CaO and TiO2 contents in the CaO-TiO2 -Fe2O3 system. The formation mechanism of Ca3TiFe2O8 is clarified:CaO reacts with Fe2O3 to form Ca2 Fe2O5, and then continues to react with the CaTiO3 to form Ca3TiFe2O8. The longer the reaction time, the greater is the amount of Ca3TiFe2O8 formed. However, the effect of temperature on the formation of Ca3TiFe2O8 is not obvious. It is found that high CaO content contributes to the formation of Ca3TiFe2O8. Further, so long as TiO2 is present, Ca3TiFe2O8 is formed under the condition of equal molar concentration Fe2O3 and CaO.
Abstract: The healing behavior of internal cracks in an ingot during the forging process was investigated using laboratory and industrial simulation studies. During the laboratory experiment, specimens with artificial cracks were hot compressed by a Gleeble simulator, and the effect of temperature and deformation ratio on inner crack healing was studied. The experimental result shows that the higher the deformation temperature or greater the deformation, the better the healing effect. To verify the accuracy and applicability of the result in an actual forging process, an industrial experiment was designed and performed. The result shows that internal cracks can be effectively metallurgically bonded at a temperature of 1200℃ and deformation ratio of 40%.
Abstract: In most steels, tin (Sn) is a tramp element due to its hot shortness at grain boundaries and the surface, although Sn also has a vital influence on free-cutting steel, electrical sheets, cast iron, and stainless steel. If the problem of hot shortness is solved, scrap recycling will become much easier and Sn can even be used as an important alloying element. As such, it is most important to investigate the forms of Sn precipitation in C-Mn steels at high temperatures. In this study, Fe-5% Sn and Fe-1.5% Sn-0.2% S steels were investigated to clarify the types of Sn precipitates. The morphology, size, and structure of Sn precipitates were characterized by scanning electron microscopy with energy dispersive spectroscopy and transmission electron microscopy. The influence of heat treatment temperature on the type of Sn precipitates was also investigated. The results show that Sn-riched particles precipitate at grain boundaries and in grains in Fe-5% Sn steels, whereas in Fe-1.5% Sn-0.2% S steels, heterogeneous Sn particles precipitate in the size of spherical MnS inclusions with diameters ranging between 2-4 μm. The transmission electron microscopy analysis and heat treatment experimental results show a FeSn2 structure with a tetragonal system for Sn precipitates in Fe-5% Sn and Fe-1.5% Sn-0.2% S steels.
Abstract: For realizing complicated shapes of the inner cavity of zinc alloy castings by pressure die casting, the problem of poor leachability has to be solved and the high-strength requirement of the water-soluble salt core should be met. High-melting potassium chloride salt and low-melting potassium nitrate salt were used as the core materials. High-strength binary composite water-soluble salt core (WSSC) was formed by the process of melting and gravity pouring. The performance characteristics of the potassium chloride core, potassium nitrate core, and binary composite WSSC (20% KCl-80% KNO3) were investigated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies were performed to examine the micro-morphology and phase composition of WSSC. The results indicate the following:the binary composite WSSC has excellent comprehensive performance, its bending strength can exceed 21.2 MPa, the 24 h hydroscopicity rate is 0.568%, the water-soluble rate can exceed 208.63 kg·min-1·m-3 in water at 80℃ and its surface has no cracks and folds unlike the pure salt core. Crack growth in the binary composite salt core occurs by deflection, which is the main reason for the improvement in bending strength.
Abstract: The wear and wear mechanisms of two typical gun barrel steels at room temperature, 200, 400, and 600℃ were investigated by wear, high-temperature hardness, and other types of tests. It was found that the friction coefficients of the two typical gun barrel steels varied little with temperature owing to the formation of triboxides. The wear rate of 32Cr2MoVA first decreased, then increased, and finally decreased with increasing temperature, whereas the wear rate of 30SiMn2MoVA first decreased and then increased with increasing temperature, reaching its maximum at 600℃. The triboxides on the wear surface depended on the temperature, the hardness of the gun barrel steel, and the difference between disc and pin hardness (Hd-Hp) at high temperatures. The temperaturedependent wear of both gun barrel steels depends on the triboxides up to 200℃. Adhesive wear prevailed with simultaneous abrasive wear at room temperature, whereas mild oxidative wear was dominant at 200℃ in both steels. The wear depends on the hardness of the gun barrel steels and disc at 400℃. Severe oxidative wear was dominant at 400℃ in both steels. At 600℃, thick and compact triboxides formed at the wear surface of 32Cr2MoVA owing to the decreasing Hd-Hp; consequently, mild oxidative wear became the dominant mechanism. For 30SiMn2MoVA, the extrusion of pin material, which is attributed to the abrupt increase in Hd-Hp, suggests that extrusion wear prevailed.
Abstract: Unlike the traditional oil-lubricated bearing, the water-lubricated bearing has unique advantages because of which lead it has important applications in all types of high-speed rotating machinery. Under actual working conditions, the lubrication water will inevitably mix with a certain amount of undissolved gas, which too will participate in the lubrication process. In this study, computational fluid dynamics (CFD) software Fluent was used to analyze the characteristics of the high-speed water-lubricated bearing and to investigate the influence of the amount of undissolved gas on the phase distribution of the gas phase, pressure peak value, and bearing performance. The full cavitation model and gas-liquid mixture model were employed in this study. The results show that in the highspeed water-lubricated bearing clearance, the gas phase is distributed in the divergence wedge, and the maximum gas volume fraction exists on the surface of the shaft; When the eccentricity is small, a certain amount of undissolved gas can offset the gas phase distribution in the bearing gap and reduce the load-carrying capacity of the bearing. However, the gas appears to have no clear influence on the pressure peak and the frictional power consumption. As the bearing eccentricity increases, the influence of the undissolved gas disappears gradually.
Abstract: For an accurate prediction of the friction experienced by the linear rolling guide and the factors affecting it, the fluid lubrication state of the rail was considered, and the effect of the friction of the linear guide on the ball contact angle and preload was studied based on the Hertz contact theory. Based on the Hertz contact theory, the static equations and the ball-raceway contact mechanics equations of the linear rolling guide were established for vertical loading. Using the Hertz contact theory, changes in the ball contact force of the linear rolling guide were analyzed. Combining the analysis of the critical load and the oil film obstruction between the balls and the rail, a friction model was established for studying the effect of the external load. Experiments were carried out on a domestic model of the linear rolling guide to validate the developed friction model. Through the analysis and comparison of the experimental and theoretical data, the influence of the resistance of the lubricating oil film, the contact angle, and the preload on the friction of the linear guide were verified. The results show that the friction of the linear rolling guide, under the condition of lubrication, is affected by the contact angle and the preload force.
Abstract: This paper proposes an algorithm that is effective in detecting the key frame of microexpression based on the entropy of oriented optical flow. Initially, this paper used an improved Horn-Schunck optical flow to extract the motion features of adjacent frames. Then, the threshold algorithm was used to filter the optical flow vectors with high-projective modulus. To capture the key frame of microexpression, the paper used information entropy to count the direction of optical flow vectors and analyzed the changing of microexpressions using an entropy vector of video sequences. Finally, the algorithm in this paper was verified with microexpression database SMIC (Oulu University) and CASME (the Director of the Institute of Psychology at the Chinese Academy of Sciences, Fu Xiaolan). Compared with traditional frame differences, experiments show that the algorithm is good not only in expressing the trend of the microexpression but also in providing the basis for microexpression recognition.
Abstract: For the segmentation of a remote sensing image, the seeded region growing algorithm is a common method. The traditional single-seed region growing algorithm can only segment a remote sensing image in a single, continuous object with simple texture. However, in the case of a high-resolution remote sensing image with complex texture and multispectral features, the segmentation result of this algorithm is unsatisfactory, as it cannot segment multiple objects simultaneously and effectively. To solve this problem, this paper proposes an improved object-oriented automatic multiseed region growing algorithm, which is suitable for simultaneously extracting multiple target objects and its segmentation result is also good. The method first uses an improved median filter to smooth the image, making the interior of the multiple target objects homogeneous, while preserving their texture. Then, it automatically selects the multiple seed regions through a certain criterion and finally, processes the grown regions and combines them. Thus, this paper obtains the segmentation results of various objects. The paper uses three sets of aerial images with different spatial resolutions to carry out experiments. Compared with watershed algorithm and traditional single-seed region growing algorithm, this method can be used for global objects. It can automatically select different types of seeds with multiple features and can simultaneously segment multiple target objects, thus providing a reliable data for the object-oriented image analysis and application.
Abstract: To enable unmanned helicopters to fly autonomously in precise paths and to reduce the influence of helicopter dynamic model error, this paper proposes a hybrid controller with active disturbance rejection control (ADRC) and adaptive control for trajectory tracking. This paper proposes the model reference adaptive control strategy for the inner-loop controller. This paper uses the momentum back-propagation (MOBP) neural network algorithm to tune the parameters of the proposed inner-loop controller. This paper uses ADRC in the proposed controller for velocity control. The simulation results indicate that the proposed controller can achieve good trajectory tracking. Compared with the PID controller and cascade ADRC, the proposed hybrid controller is more robust and has better anti-disturbance capability. This paper uses the proposed hybrid controller for trajectory-tracking control of the XV-2, which is an unmanned helicopter with a gross take-off weight level of 200 kg. With the help of the hybrid controller in our flight test, the root mean square error of the XV-2 trajectory-tracking control is within 0.6 m.
Abstract: Steel frames with precast reinforced concrete infill walls are a new type of composite structures. These composite structures have excellent lateral resistance behavior because of double defense lines comprising the steel frame and infill walls. At the same time, precast members and prefabricated buildings are favorable for the development of the housing industry. Considering the difficulties in the transportation and installation of large precast RC infill walls, steel frames with vertical and horizontal combined precast RC infill wall structures were proposed, and finite element models were established by using ABAQUS to analyze the mechanical behaviors of the structures. By analyzing load-displacement curves, stress distributions, and deformations of members, the damage characteristics, and mechanical behaviors of the structure were studied. The results show that the whole bolt structure has good bearing capacity and ductility owing to its reasonable load transfer path; the vertical combined model has excellent initial stiffness and ultimate bearing capacity, similar to the whole bolt connection precast RC wall. Furthermore, the vertical combined precast RC infill wall is convenient for transportation and installation. However, the initial stiffness and ultimate bearing capacity of the horizontal combined model are both less than the corresponding values for the whole bolt model and the vertical combined model because of the lack of an effective load transfer path between the top and bottom RC walls. Hence, this horizontal model is not favorable for practical engineering applications.
Abstract: This study conducted a steel-plate buckling analysis and a stress analysis of confined core concrete in a composite shear wall with a double-skin steel plate. Using the bottom shear wall of a core tube in the Beijing Chinese Statue as a prototype, the study tested the 1/4-scale concrete composite shear wall with a double-skin steel plate and a composite shear wall with an embedded steel plate with respect to axial compression, and then compared and analyzed the axial bearing capacity and load-displacement curves. Considering the influence of steel-plate buckling on the axial bearing capacity and the improved compressive strength of confined concrete, this paper proposes a calculation formula for the bearing capacity of a composite shear wall with a double-skin steel plate. Comparing this calculated values with those of other methods, the calculated values of this proposed method fits best. Based on relevant data in the literature regarding axial compression performance tests of composite shear walls with a double-skin steel plate, the axial compressive bearing capacity values obtained by this proposed formula are in good agreement with experimental results.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
