Search

The technologies of high charge perforator and high density perforator are widely used in domestic and international oil-gas wells perforating job, which leads to the increase of the explosion load intensity, resulting in more string damage accidents, and seriously affects the normal production of oil and gas. The software of LS-DYNA was used to measure the dynamic response of the perforating gun under four types of perforation conditions. It analyzes perforating gun head's forms and characteristics of output load under different working conditions, and also analyzes the impact on perforating gun's structural strength under different axial and radial load. These conclusions provide an important theoretical reference for reasonable arranging the perforating technology, improving perforation safety and reducing the well perforating accidents.

The carbon fiber–reinforced plastics have gained considerable attention in the aerospace industry in recent years. Drilling of carbon fiber–reinforced plastic is relatively difficult with too much fiber delamination and pulling out in the entry and exit of the holes. As an advanced hole-making technology, helical milling is being developed in machining of carbon fiber–reinforced plastic, in which the tool moves on a helical course to the workpiece. Experiments were carried out on helical milling of carbon fiber–reinforced plastic, the effects of the cutting parameters and tool wear on the cutting forces are analyzed, and the relation between hole quality and cutting forces is also discussed. In order to simulate the cutting forces under different cutting conditions, the mechanistic modeling technique is used to predict cutting forces in helical milling of carbon fiber–reinforced plastic, and the cutting force coefficients are identified and corrected based on the experimental data. The results show that the established model can be used to predict the cutting forces in the helical milling process.

In this paper, in order to increase the efficiency of solar energy collection in winter, a method to set the semi-fixed collector was proposed. The best angle of the quasi-fixed solar collector have be calculated and given in Daqing region. According to comparison and analysis, we find that the efficiency improved 8.3%; it will collect solar energy 410.46 MJ per square more than fixed collectors every year.

Several studies have suggested that sodium intake may affect blood pressure (BP), proteinuria, and intrarenal transforming growth factor-β1 (TGF-β1) production in patients and animal models with chronic kidney disease (CKD). The Chinese population has a high prevalence of CKD and is well known for consuming salty foods. This study will investigate the role of dietary sodium intake on BP control among non-dialysis Chinese CKD patients.A cross-sectional study was carried out in a cohort of 176 non-dialysis hypertensive CKD patients to investigate their sodium intake and its effect on BP control by measuring 24-h urine sodium excretion (24-h UNa). A total of 20 patients with immunoglobulin A nephropathy (IgAN) participated in a 7-day sodium restriction study (100 mmol/day). Their changes in BP, proteinuria, and urinary TGF-β1 excretion were subsequently analyzed. Another 23 IgAN patients without salt restriction were included as controls.The average 24-h UNa of the study cohort was 149.0 ± 66.4 mmol/day. Only 31.8% patients had a 24-h UNa less than 100 mmol/day. The OR for each 17 mmol increment in 24-h UNa (salt 1 g/day) for BP130/80 mmHg was 1.26 (95% CI 1.10-1.44, P = 0.001). The sodium restriction group achieved significantly more reduction in SBP (-11.1 mmHg vs. -5.0 mmHg, P = 0.022), DBP (-9.4 mmHg vs. -2.1 mmHg, P = 0.009), and urine protein excretion [-465 (-855 to -340) mg/day vs. -150 (-570 to 40) mg/day, P = 0.024]. A positive correlation was observed between the change of 24-h UNa and the change of SBP (r = 0.450, P = 0.047) in the sodium restriction group. The change of 24-h UNa was also correlated with the 24-h TGF-β1 excretion (r = 0.558, P = 0.011) in these patients.Dietary sodium intake restriction should be monitored and intensified in the treatment of Chinese CKD patients.

A method both convenience for generation and calculation for anticipated ASE waveform in spun fiber Raman amplifier,by analyzing the NLSE of signal and pump wave in fiber,is proposed.According to its time domain characters,a non-Gaussian noise ASE model is established and the term is added to the NLSE simultaneously by considering birefringence rotation effect in spun fiber Raman amplifier.By solving the equation with Split Step Fourier Method,ASE in spun fiber Raman amplifier is investigated.Numerical results for the ASE noise power spectrum are validated.

As a new technology, mobile agent (MA) shows a wide application in the field of network technology. However, security has been one of the crucial problems in its application. A new protection model based on a trusted element is presented in this paper. The trusted element, which differs from the traditional trusted hardware such as a smart card or a co-processor, offers a third party service based on an encrypted circuit construction. The procedure of constructing an encrypted circuit is introduced and the method of using the trusted service to protect the MA is also described. An application example is given to show how to use the new model at the end of the paper.

As the traditional methods were not suitable for the detection of small distribute denial of service (DDoS) attack and identification of busy traffic, on the basis of the influence of DDoS attack, one wavelet analysis method was proposed. Wavelet method of coefficient variance analysis was deduced and a software model for the method was designed. In addition, key issues of the choice of wavelet and calculation of Hurst were resolved. The experimental results show that the proposed method has more advantages in accurately identifying busy traffic and detection of small DDoS attack.

most research literature pays attention to the contract coordination of the two-stage supply chain, however supply chain often consists of more than two separate firms. This paper aims to study the coordination issue of a three-stage supply chain selling short life cycle products in a single period model. The combined contracts mechanism that a buy-back contract between the retailer and the distributor and a revenue-sharing contract between the manufacture and the distributor cannot coordinate the channel under random demand while these two processes use the same quantity discount contract can coordinate the three-stage supply chain. We show that the three-stage supply chain can be fully coordinated by designing appropriate contract parameters.

With the increasing of the private enterprises overseas listing, the study of motivation of private enterprises overseas listing attracted widely attention. This paper proposes motivation hypothesis of private enterprise overseas listing; then use empirical research methods of collecting data, select variables, establish a Logit model. The Empirical results showed that Private enterprise overseas listing has significant financial motivation, Corporate Governance motivation, maximizing shareholder wealth motivation, Security and equal motivation motivation.

The traditional methodology on risk analysis in construction project feasibility research has remained for a long time in the atmosphere of qualitative analysis. A thorough quantitative analysis approach in the same field has been carried out in this paper based on the properties and mechanisms of value mining. Taking advantages of value mining theory, the practical evaluation on potential revenue and predictable risk of construction project has been put forward, and the optimization among various schemes for construction project feasibility research is proposed, under the principles of multi-target fuzzy decision making and satisfaction degree of value mining.

Based on scale free network, the public opinion evolution model is constructed, in which the public opinion changes with topology (the relationship and the influence between the individual). The model features that the network structure constantly changes in the process of evolution with evolution parameter φ0. It is found that the evolution of the public opinion not only is controlled by the topological structure, but also induces the change of the topological structure: the network structure is no longer the initial scale-free network,but it has a Poisson distribution. With the time evolution in system, there is obvious convergence effect of the public opinions. The dozens of opinions in initial state evolve with time, but most of them perish and only a few of them can survive and develop for a long time. The evolution trend is coincident with that of the public opinions, views and beliefs in society.

The poled PZT 95/5 ferroelectric ceramic is in ferroelectric (FE) phase, it can be transformed into the antiferroelectric (AFE) phase by shock compression, so the bound charge can be liberated into an external circuit to generate pulses of electrical current. Based on this FE/AFE transition theory, the electrical response of LRC load was discussed, especially for the small resistance (R) and small inductance (L) load in this paper. A set of PZT 95/5 ceramics in parallel connection was devised to generate large pulses of electrical current in two plane-wave tests. The maximum output current reaches above 5 kA, and the corresponding rise time of the front edge is under 500ns.

The characteristics of terahertz (THz) radiations from the surfaces of two kinds of narrow-band semiconductors InN and InAs excited by femtosecond laser pulses with different pump powers (from 10 to 320mW) are investigated experimentally. The results show that InAs can irradiate a stronger THz signal than that of InN under the same pump power so its radiation efficiency is higher. However, the spectral widths of THz radiations from these semiconductor surfaces increase with the increase of pump power. When the intensity of pump laser is high enough, the spectral Half-Maximum-Full-Width (HMFW) of THz radiation tends to be a constant. Compared with InAs, InN can reach this constant HMFW THz spectrum at a lower pump power. This research is significant for investigating the THz radiation mechanism from semiconductor surfaces, and it is also a good reference for exploring a THz radiation source with low cost and high efficiency.