Soil in a cold region is subject to frequent freezing and thawing cycles. Soil frozen for a prolonged period may cause adverse freeze damage to the plants due to cell dehydration or root cell rupture. It is important to understand the detailed heat transfer behaviors of the freezing and thawing processes to prevent freeze damage, and to devise proper mitigation measures for effective pot planting in cold regions. A theoretical model was developed to analyze the transient moving phase-change interface heat transfer in the freezing and thawing of porous potting soil. The theoretical derivation is based on the assumption that the soil freezes completely at a single temperature. Microscopic poromechanic effects on heat transfer behavior were ignored. The spatial domain of the problem was simplified to a 1D spherical coordinate system with variation in the radial direction. Green’s function was applied to solve for the time-dependent body temperature. Experiments were conducted for validation of the theoretical model. Reasonable agreement between the theoretical predictions and experimental measurements was obtained. The theoretical model developed can be easily used to determine the sensitivity of various parameters in the freezing/thawing processes, e.g., thermal properties of soil, ambient temperature, and planting pot size.

The micro-Raman method is a non-contact and non-destructive method for thermal conductivity measurement. To reduce the measurement error induced by the poor fit of the basic equation of the original micro-Raman method, we developed a new basic equation for the heat source of a Gaussian laser beam. Based on the new basic equation, an analytical heat transfer model has been built to extend the original micro-Raman method to thin films with submicrometer- or nanometer-scale thickness. Experiments were performed to measure the thermal conductivity of dielectric thin films with submicrometer- or nanometer-scale thickness. The thermal resistance of the interface between dielectric thin films and their silicon substrate was also obtained. The obtained thermal conductivity of silicon dioxide film is 1.23 W/(m·K), and the interface thermal resistance between silicon dioxide film and substrate is 2.35×10⁻⁸ m²·K/W. The thermal conductivity and interface thermal resistance of silicon nitride film are 1.07 W/(m·K) and 3.69×10⁻⁸ m²·K/W, respectively. The experimental results are consistent with reported data.

We report an experimental investigation on the impact of the freezing rate on the cryo-deformation and cryo-damage of cementitious materials. Saturated, dried and air-entrained mortar specimens are subjected to laboratory freeze-thaw cycles under three freezing rates without moisture exchange with the environment. In addition to basic mechanical properties and pore distribution, the measurement is also effectuated for freezing expansion, residual deformation of the specimens in each cycle. From the results it is observed that a high freezing rate does augment the freezing expansion of material while the cryo-damage is more important for a low freezing rate. Accordingly, both the freezing rate and freezing duration should be taken into account for the cyro-damage extent of cementitious materials.

We proposed an optimal design method to expand the bandwidth for the control of large hydraulic Stewart platform. The method is based on generalized natural frequency and takes hydraulic oil into consideration. A Lagrangian formulation which considers the whole leg inertia is presented to obtain the accurate equivalent mass matrix. Using the model, the effect of leg inertia and the influence of design parameters on the generalized natural frequency are investigated. Finally, numerical examples are presented to validate and confirm the efficiency of the mathematical model. The results show that the leg inertia, especially the piston part plays an important role in the dynamics. The optimum diameter ratio of the base to the moving platform is between 2 and 3, and the optimum joint angle ratio of the base to the moving platform is about 1. The smaller joint angles and a longer leg stroke are favorable for raising system frequencies. The system oil should be preprocessed for large platforms with a requirement for good dynamic performance.

A single screw compressor (SSC) is an important component found in many refrigeration systems. However, the durability is not so good because of the friction between its meshing pair. Therefore the column envelope meshing pair was proposed to prolong the operating life of SSCs, although it has not been applied to commercial refrigeration systems. To accelerate the industrial application, a mathematical model for analyzing the column envelope meshing pair is established based on the geometry and kinematics. Equations giving the flanks of column envelope grooves are obtained, and teeth flank meshing with the groove is designed. Results show that this model could be applicable in the design of the column envelope type SSC.

In this paper the residual stresses in a butt-welded plate of 2.25Cr 1Mo has been analyzed using a 3D and transient finite element (FE) model. Also the effect of the welding-electrode speed has been studied using death and birth of FEs. For this purpose, a coupled thermo-mechanical FE solution has been used to obtain the temperature distribution and the resulting residual stresses. Also, the variations of the physical properties of the material with temperature have been taken into account. Results show that the residual stresses in the heat affected zone (HAZ) are maximum and change along the weld and also in the plate-thickness. It has been shown that use of the 3D and transient model will lead to more accurate and realistic results which are well compared with the experimental test data.

This paper presents a method to create concept models for the tapered thin-walled tubes using beam elements and spring elements. Developed concept tapered beam models with different taper angles and cross sections are compared with those detailed models through impact analyses. Important crash results are recorded and compared, and the relatively good agreement is achieved between these analyses. Concept modeling steps are illustrated in detail, and a general concept modeling method for such thin-walled tubes is summarized and presented.

We studied the response of harmonically and stochastically excited strongly nonlinear oscillators with delayed feedback bang-bang control using the stochastic averaging method. First, the time-delayed feedback bang-bang control force is expressed approximately in terms of the system state variables without time delay. Then the averaged Itô stochastic differential equations for the system are derived using the stochastic averaging method. Finally, the response of the system is obtained by solving the Fokker-Plank-Kolmogorov (FPK) equation associated with the averaged Itô equations. A Duffing oscillator with time-delayed feedback bang-bang control under combined harmonic and white noise excitations is taken as an example to illustrate the proposed method. The analytical results are confirmed by digital simulation. We found that the time delay in feedback bang-bang control will deteriorate the control effectiveness and cause bifurcation of stochastic jump of Duffing oscillator.

We studied the problem of bifurcation and chaos in a 4-side fixed rectangular thin plate in electromagnetic and mechanical fields. Based on the basic nonlinear electro-magneto-elastic motion equations for a rectangular thin plate and the expressions of electromagnetic forces, the vibration equations are derived for the mechanical loading in a steady transverse magnetic field. Using the Melnikov function method, the criteria are obtained for chaos motion to exist as demonstrated by the Smale horseshoe mapping. The vibration equations are solved numerically by a fourth-order Runge-Kutta method. Its bifurcation diagram, Lyapunov exponent diagram, displacement wave diagram, phase diagram and Poincare section diagram are obtained.

Aiming at exploring the excellent structural performance of the vein-stiffening membrane structure of dragonfly hind wings, we analyzed two planar computational models and three 3D computational models with cambered corrugation based on the finite element method. It is shown that the vein size in different zones is proportional to the magnitude of the vein internal force when the wing structure is subjected to uniform out-of-plane transverse loading. The membrane contributes little to the flexural stiffness of the planar wing models, while exerting an immense impact upon the stiffness of the 3D wing models with cambered corrugation. If a lumped mass of 10% of the wing is fixed on the leading edge close to the wing tip, the wing fundamental frequency decreases by 10.7%~13.2%; if a lumped mass is connected to the wing via multiple springs, the wing fundamental frequency decreases by 16.0%~18.0%. Such decrease in fundamental frequency explains the special function of the wing pterostigma in alleviating the wing quivering effect. These particular features of dragonfly wings can be mimicked in the design of new-style reticulately stiffening thin-walled roof systems and flapping wings in novel intelligent aerial vehicles.

We investigated the structural behavior and bearing capacity of system scaffolds. The research showed that the critical load of a system scaffold structure without diagonal braces is similar to that of a door-shaped steel scaffold structure. Joint stiffness between vertical props in system scaffolds can be defined based on a comparison between analytical and experimental results. When the number of scaffold stories increases, the critical loads of system scaffolds decrease. Diagonal braces markedly enhance the critical load of system scaffolds. The coupling joint position between vertical props should be kept away from story-to-story joints to prevent a reduction in critical loads. The critical load of a system scaffold decreases as the quantity of extended vertical props at the bottom of the structure increases. A large Christmas tree set up by system scaffolds under various loads was used as an example for analysis and to check the design of system scaffolds.

The settlement curve of the foundation endured the ramp load is an S-type curve, which is usually simulated via Poisson curve. Aimed at the difficulty of preferences in Poisson curve, an immune algorithm (IA) is used. IA is able to obtain a multiple quasi-optimum solution while maintaining the population diversity. In this paper, IA is used in an attempt to obtain accurate settlement prediction. The predicted settlements obtained by IA are compared with those predicted by the least squares fitting method (LSM), the Asaoka method and the genetic algorithm (GA). The results show that IA is a useful technique for predicting the settlement of foundations with an acceptable degree of accuracy and has much better performance than GA and the Asaoka methods.

An artificial intelligence technique of back-propagation neural networks is used to assess the slope failure. On-site slope failure data from the South Cross-Island Highway in southern Taiwan are used to test the performance of the neural network model. The numerical results demonstrate the effectiveness of artificial neural networks in the evaluation of slope failure potential based on five major factors, such as the slope gradient angle, the slope height, the cumulative precipitation, daily rainfall and strength of materials.

Aluminum nitride (AlN)/borosilicate glass composites were prepared by the tape casting process and hot-press sintered at 950 °C with AlN and SiO₂-B₂O₃-ZnO-Al₂O₃-Li₂O glass as starting materials. We characterized and analyzed the variation of the microstructure, bulk density, porosity, dielectric constant, thermal conductivity and thermal expansion coefficient (TEC) of the ceramic samples as a function of AlN content. Results show that AlN and SiO₂-B₂O₃-ZnO-Al₂O₃-Li₂O glass can be sintered at 950 °C, and ZnAl₂O₄ and Zn₂SiO₄ phase precipitated to form glass-ceramic. The performance of the ceramic samples was determined by the composition and bulk density of the composites. Lower AlN content was found redounding to liquid phase sintering, and higher bulk density of composites can be accordingly obtained. With the increase of porosity, corresponding decreases were located in the dielectric constant, thermal conductivity and TEC of the ceramic samples. When the mass fraction of AlN was 40%, the ceramic samples possessed a low dielectric constant (4.5~5.0), high thermal conductivity (11.6 W/(m·K)) and a proper TEC (3.0×10⁻⁶ K⁻¹, which matched that of silicon). The excellent performance makes this kind of low temperature co-fired ceramic a promising candidate for application in the micro-electronics packaging industry.

A method for fabricating arrays of microcapsules covalently immobilized onto chemically patterned substrates was developed. The core-shell microparticles with poly(allylamine hydrochloride) (PAH) as the outermost layer were obtained by layer-by-layer (LbL) assembly, which were further treated with glutaraldehyde to endow the particles with abundant aldehyde groups on their surfaces. The particles were then covalently coupled to the chemically patterned regions with amino groups created by microcontact printing (μCP). After dissolution of the core particles, arrays of the hollow microcapsules with unchanged structures were obtained. These arrays could stand rigorous environmental conditions of higher ionic strength, and lower and higher pH values. Thus, the technique could be possibly applied to exploiting chips of microcontainers or microreactors in sensing technology.

To understand the feasibility of its application to the in situ remediation of contaminated groundwater, the dechlorination of 2,4-dichlorophenol (2,4-DCP) by Ni/Fe nanoparticles in the presence of humic acid (HA) was investigated. We found that, as high performance liquid chromatography (HPLC) was used, the 2,4-DCP was first quickly reduced to o-chlorophenol (o-CP) and p-chlorophenol (p-CP), and then reduced to phenol as the final product. Our experimental results indicated that HA had an adverse effect on the dechlorination of 2,4-DCP by Ni/Fe nanoparticles, as the HA concentration increased, the removal rate decreased evidently. It also demonstrated that 2,4-DCP was reduced more easily to o-CP than to p-CP, and that the sequence of the tendency in dechlorination of intermediates was p-CP>o-CP. Transmission electron microscope (TEM) showed that HA could act as an adsorbate to compete reactive sites on the surface of Ni/Fe nanoparticles to decrease the dechlorination rate. Also we concluded that the dechlorination reaction of 2,4-DCP over Ni/Fe nanoparticles progressed through catalytic reductive dechlorination.

Decomposition of dimethyl sulfide (DMS) in air was investigated experimentally by using a wire-cylinder dielectric barrier discharge (DBD) reactor at room temperature and atmospheric pressure. A new type of high pulse voltage source with a thyratron switch and a Blumlein pulse-forming network (BPFN) was adopted in our experiments. The maximum power output of the pulse voltage source and the maximum peak voltage were 1 kW and 100 kV, respectively. The important parameters affecting odor decomposition, including peak voltage, pulse frequency, gas flow rate, initial concentration, and humidity, which influenced the removal efficiency, were investigated. The results showed that DMS could be treated effectively and almost a 100% removal efficiency was achieved at the conditions with an initial concentration of 832 mg/m³ and a gas flow rate of 1000 ml/min. Humidity boosts the removal efficiency and improves the energy yield (EY) greatly. The EY of 832 mg/m³ DMS was 2.87 mg/kJ when the relative humidity was above 30%. In the case of DMS removal, the ozone and nitrogen oxides were observed in the exhaust gas. The carbon and sulfur elements of DMS were mainly converted to carbon dioxide, carbon monoxide and sulfur dioxide. Moreover, sulfur was discovered in the reactor. According to the results, the optimization design for the reactor and the matching of high pulse voltage source can be reckoned.

To explore the applicability of anoxic-oxic (A/O) activated sludge process for petrochemical wastewater treatment, the relationship between bacterial community structure and pollutants loading/removal efficiencies was investigated by gas chromatograph-mass spectrometry (GC-MS), polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and other conventional techniques. It showed that when the concentrations of the influent chemical oxygen demand (COD) and ammonia nitrogen (NH₄⁺-N) were 420~560 mg/L and 64~100 mg/L, respectively, the corresponding average effluent concentrations were 160 mg/L and 55 mg/L, which were 1.6 and 2.2 times higher than those of the national standards in China, respectively, demonstrating the inefficient performances of A/O process. Analysis of GC-MS indicated that refractory pollutants were mainly removed by sludge adsorption, but not by biodegradation. PCR-DGGE profile analysis suggested that the biological system was species-rich, but there was apparent succession of the bacterial community structure in different locations of the A/O system. Variations of bacterial community structure and pollutant loadings had obvious influences on pollutants removal efficiencies. Thus, A/O process was inapplicable for the treatment of complicated petrochemical wastewater, and strategies such as the reinforcement of pre-treatment and two-stage A/O process were suggested.

In order to analyze the characteristics of surface water resource quality for the reconstruction of old water treatment plant, multivariate statistical techniques such as cluster analysis and factor analysis were applied to the data of Yuqiao Reservoir— surface water resource of the Luan River, China. The results of cluster analysis demonstrate that the months of one year were divided into 3 groups and the characteristic of clusters was agreed with the seasonal characteristics in North China. Three factors were derived from the complicated set using factor analysis. Factor 1 included turbidity and chlorophyll, which seemed to be related to the anthropogenic activities; factor 2 included alkaline and hardness, which were related to the natural characteristic of surface water; and factor 3 included Cl and NO₂-N affected by mineral and agricultural activities. The sinusoidal shape of the score plots of the three factors shows that the temporal variations caused by natural and human factors are linked to seasonality.

Journal of Zhejiang University-SCIENCE A (JZUS-A), its former version named Journal of Zhejiang University-SCIENCE (ISSN 1009-3095), has been covered by Science Citation Index Expanded (SCI-E) since 2007. Till now, all the 500 papers pub-lished in JZUS-A during 2007 and 2008 have been abstracted and indexed into Web of Science.\nIn 2008, we have been striving to further im-prove the internationalization and the paper quality of JZUS-A. Our work mainly includes: (1) We adopted Editorial Manager^TM online submission system (http://www.editorialmanager.com/zusa/), which greatly advances the peer review process and also leads to an unexpected trust between the peer reviewers/authors and the journal. (2) We joined in CrossCheck^TM as the first member in China, which is a new anti-plagiarism tool released by CrossRef to verify and protect the originality and copyright of submitted manuscripts.