A novel polycarbonate urethane was synthesized by the two-stage solution process of diisocyanates with polycarbonate diols (PCDL), in which PCDL, 1,4-butanediol (BD) and mixture of 4,4′-methylenediphenyl diisocyanate and hexamethylene diisocyanate (HDI) were soft segment, chain extender and rigid segment, respectively. The structures were characterized by using FTIR and 1H-NMR. The thermoanalysis and mechanical properties of products were measured by means of DSC, TG and other systems. The result shows that an important technological thrust is the development of polymeric materials with improved mechanical characteristics. With the increase in content of HDI component, the elongation at break point increases quickly and decomposition temperature decreases. The DSC/TG curves indicate that a phase division exists in the structure of polycarbonate urethanes. Thermal decomposition occurs at two temperature levels because their rigid and soft chain segments correspond to different glass transition domains, respectively. This paper demonstrates that the mechanical properties of polycarbonate urethane can be controlled by changing the ratio of raw materials.
In this paper, the sensors array technique is applied to the quality detection of aluminum alloy spot welding. The sensors array has three forms, i.e., linear magnetic sensors array, annular magnetic sensors array and cross magnetic sensors array. An algorithm based on principal component analysis is proposed to extract the signal eigenvalues. The three types of magnetic sensors array are used in the experiment of monitoring the signal. After the eigenvalues are extracted, they are used to build a relationship with the nugget information. The result shows that when the distance between the core of the array and the pole is 60 mm, the arrays work best. In this case, when the eigenvalues’ range of the linear array is 0.006 5–0.015 1, the quality of the spots is eligible. To the annular and cross array, when the ranges are 0.082 9–0.131 6 and 0.085 1–0.098 2 respectively, the nugget quality is eligible.
A pilot-scale ultrafiltration membrane plant was set up for treating Luanhe River water with flocculating and precipitation process of waterworks. The aim is to investigate the variation and characteristics of natural organic matter and disinfection byproducts formation potential in the whole process in winter. The results show that dissolved organic matter (DOM), UV254, trihalomethanes formation potential (THMsFP) and haloacetic acids formation potential (HAAsFP) of Luanhe River water were mainly distributed in the range of molecular weight (MW) <1 kDa, so were the membrane feed water and treated water by membrane. Specific UV absorbance, specific THMsFP and specific HAAsFP have the maximal value in the MW fraction of 1–3 kDa, except that specific UV absorbance of membrane feed water is in the range of 3–10 kDa; DOM of membrane backwash water is mainly distributed in the range of MW>30 kDa and MW<1 kDa. It is the DOM in water backwashing in up way that made significant contribution to the higher dissolved organic carbon content in membrane backwash water. However, UV254, THMsFP and HAAsFP were mainly distributed in the range of MW<1 kDa. The highest concentrations of specific THMsFP and specific HAAsFP appeared in the MW fraction of 3–10 kDa. CHCl3 was the major THMs species during MBW chlorination and occupied more than 60% of the total THMsFP. Dichloroacetic acid and trichloroacetic acid were the main components in HAAsFP. The concentration of THMsFP and HAAsFP in MBW was influenced by operation period.
Based on the maximum flux principle (MFP), a water quality evaluation model for surface water ecosystem is presented by using self-organization map (SOM) neural network simulation algorithm from the aspect of systematic structural evolution. This evaluation model is applied to the case of surface water ecosystem in Xindu District of Chengdu City in China. The values reflecting the water quality of five cross-sections of the system at different developing stages are obtained, with stable values of 1.438, 2.952, 1.869, 2.443 and 2.479, respectively. The simulation also indicates that the larger the value, the more serious the water pollution. Furthermore, a classification graph is given to reflect the evolution of structural pattern. The combination of MFP and SOM neural network reveals the formation of different structural patterns in the system during the interaction of internal components. It is shown that a dominant pattern is finally reserved, which starts from a variety of combination patterns for a time period. The results agree with those from traditional evaluation methods, which indicates that the proposed model has high accuracy. This model embodies the evolutionary dynamic mechanisms and characteristics of temporal and spatial changes, which helps to guide the prediction of water quality status of surface water ecosystem.
A low cost of die area and power consumption CMOS image sensor readout circuit with fixed pattern noise (FPN) cancellation is proposed. By using only one coupling capacitor and switch in the double FPN cancelling correlative double sampling (CDS), pixel FPN is cancelled and column FPN is stored and eliminated by the sample-and-hold operation of digitally programmable gain amplifier (DPGA). The bandwidth balance technology based on operational amplifier (op-amp) sharing is also introduced to decrease the power dissipation of traditional multi-stage switched capacitor DPGA. The circuit is designed and simulated using 1P6M 0.18 μm 1.8 V/3.3 V process. Simulation results indicate that the proposed CDS scheme can achieve an FPN of less than 1 mV. The total sampling capacitor per column is 0.9 pF and no column-wise power is dissipated. The die area and FPN value are cut by 70% and 41% respectively compared with amplifier-based CDS. The op-amp sharing gain stage can achieve a 12-bit precision and also implement an 8-bit gain controlling within a gain range of 24 dB. Its power consumption is 1.4 mW, which is reduced by 57% compared with traditional schemes. The proposed readout circuit is suitable for the application of low power cost-sensitive imaging systems.
High resistance thin film chip resistors (0603 type) were studied, and the specifications are as follows: 1 kΩ with tolerance about ±0.1% after laser trimming and temperature coefficient of resistance (TCR) less than ±15×10−6/°C. Cr-Si-Ta-Al films were prepared with Ar flow rate and sputtering power fixed at 20 standard-state cubic centimeter per minute (sccm) and 100 W, respectively. The experiment shows that the electrical properties of Cr-Si-Ta-Al deposition films can meet the specification requirements of 0603 type thin film chip resistors when the deposition time was about 11 min and deposition films were annealed at 500 °C for 120 min. The morphologies of Cr-Si-Ta-Al film surfaces were examined by scanning electron microscopy (SEM). The analysis suggests that Ta and Al may be distributed in CrSi2 film with mixed form of several structures (e.g., bridge-like, capillary-like or island-like structures), and such a structure distribution is responsible for high film resistance and low TCR of Cr-Si-Ta-Al film.
By using hyper-graph theory, this paper proposes a QoS adaptive topology configuration (QATC) algorithm to effectively control large-scale topology and achieve robust data transmitting in synchronous wireless sensor networks. Firstly, a concise hyper-graph model is abstracted to analyze the large-scale and high-connectivity network. Secondly, based on the control theory of biologic “Cell Mergence”, a novel self-adaptive topology configuration algorithm is used to build homologous perceptive data logic sub-network for data aggregation. Compared with Flooding, Directed Diffusion, and Energy Aware Directed Diffusion protocols, the simulation proved that QATC algorithm can save more energy, e.g., about 23.7% in a large size network, and has less delay than the other algorithms. In dynamic experiments, QATC keeps a robust transmitting quality with 10%, 20% and 30% random failure nodes.
The problem of adaptive multi-objective optimization (AMOO) has received extensive attention due to its practical significance. An important issue in optimizing a multi-objective system is adjusting the weighting coefficients of multiple objectives so as to keep track of various conditions. In this paper, a feedback structure for AMOO is designed. Moreover, the reinforcement learning combined with hidden biasing information is applied to online tuning weighting coefficients of objective functions. Finally, the proposed approach is applied to the optimization design problem of an elevator group control system. Simulation results show that AMOO has the best average performance at up-peak traffic profile, and its average waiting time reaches 22 s. AMOO is suitable for various traffic patterns, and it is also superior to the majority of algorithms at down-peak traffic profile.
The aim of this paper is to propose a useful method for exploring regional ventilation and perfusion in the chest and also separation of pulmonary and cardiac changes. The approach is based on estimating both electrical impedance tomography (EIT) measurements and reconstructed images by means of principal component analysis (PCA). In the experiments in vivo, 43 cycles of heart-beat rhythm could be detected by PCA when the volunteer held breath; 9 breathing cycles and 50 heart-beat cycles could be detected by PCA when the volunteer breathed normally. The results indicate that the rhythms of cardiac activity and respiratory process can be exploited and separated through analyzing the boundary measurements by PCA without image reconstruction.
Fiber Bragg grating (FBG) is used as a wavelength reference device to calibrate the position of gas absorption peak in the intracavity absorption gas sensor (ICAGS) based on erbium-doped fiberring laser. This system can detect both the reflectance spectrum of FBGs and absorption spectrum of measured gas during a single wavelength sweeping process by linearly varying the driving voltage of optic filter. The voltages corresponding to center wavelength positions of four FBGs in the spectrum are determined through Gaussian peak fitting. Then, the wavelengths of gas absorption lines are deduced from the correspondence between driving voltage and wavelength obtained by quadratic curve fitting. The maximum error of wavelength of acetylene absorption lines between experimental results and those from HITRAN database is 0.106 nm and the resolving accuracy of two adjacent absorption lines is about 93.593%. By using this method, ICAGS can theoretically recognize the measured gas type and monitor multi-gas components.
This paper presents a new genetic algorithm for the resource-constrained project scheduling problem (RCPSP). The algorithm employs a standardized random key (SRK) vector representation with an additional gene that determines whether the serial or parallel schedule generation scheme (SGS) is to be used as the decoding procedure. The iterative forward-backward improvement as the local search procedure is applied upon all generated solutions to schedule the project three times and obtain an SRK vector, which is reserved into population. Several evolutionary strategies are implemented including the elitist selection (the high quality solution set), and the selection of parents used in crossover operator. The computational experiments on 1 560 standard instances show that the proposed algorithm outperforms the current state-of-the-art heuristic algorithms for J30 and J60, and ranks the third for J120 with 50 000 schedules; it ranks the second for J30 and J60, and ranks the fifth for J120 with 5 000 schedules; it ranks the third, second, and fifth for J30, J60 and J120 with 1 000 schedules, respectively. It is demonstrated that the proposed algorithm is competitive for RCPSP, especially for larger number of schedules.
The loss of life risk evaluation model for dam break is built in this paper. By using an improved Monte Carlo method, the overtopping probability induced by concurrent flood and wind is calculated, and the Latin Hypercube Sampling is used to generate random numbers. The Graham method is used to calculate the loss of life resulting from dam failure. With Dongwushi reservoir located at Hebei Province taken as an example, the overtopping probability induced by concurrent flood and wind is calculated as 4.77×10−6. Loss of life is 24 220 when the warning time is 0.25–1 h and flood severity understanding is vague, which indicates that the risk is intolerable. The losses of life under three other conditions are tolerable: warning time 0.25–1 h, and precise flood severity understanding; warning time more than 1 h, and vague flood severity understanding; warning time more than 1 h, and precise flood severity understanding.
To overcome the excessive computational cost and/or bad accuracy of traditional approaches, the probabilistic density evolution method (PDEM) is introduced. The dynamic reliability of a double-layer cylindrical latticed shell is evaluated by applying PDEM and Monte Carlo Method (MCM) respectively, and four apparent wave velocities (100 m/s, 500 m/s, 800 m/s and 1 200 m/s) and five thresholds (0.1 m, 0.2 m, 0.3 m, 0.4 m and 0.5 m) are taken into consideration. Only the difference between threshold and maximal deformation is taken as the performance function. The numerical results show that results obtained by PDEM and MCM agree well; the dynamic reliability increases markedly with the increase of displacement threshold; the types of probabilistic density curves of response are different from that of regular distribution; the dynamic reliability will decrease with the decrease of apparent wave velocity, and more members will enter into the plastic state when subjected to multi-support excitations compared with uniform excitation. Thus, it is necessary to take the wave passage effect into consideration in the seismic design of shell structures.