Effect of stress level on fatigue behavior of 2D C/C composites

Laminated carbon fiber clothes were infiltrated to prepare carbon fiber reinforced pyrolytic carbon （C/C） using isothermal chemical vapor infiltration （CVI）. The bending fatigue behavior of the infiltrated C/C composites was tested under two different stress levels. The residual strength and modulus of all fatigued samples were tested to investigate the effect of maximum stress level on fatigue behavior of C/C composites. The microstructure and damage mechanism were also investigated. The results showed that the residual strength and modulus of fatigued samples were improved. High stress level is more effective to increase the modulus. And for the increase of flexural strength, high stress level is more effective only in low cycles. The fatigue loading weakens the bonding between the matrix and fiber, and then affects the damage propagation pathway, and increases the energy consumption. So the properties of C/C composites are improved.

ON THE OPTIMIZATION OF VLSI ALLOCATION IN HIGH-LEVEL SYNTHESIS

Allocation is one of main tasks in the high-level synthesis. It includes module , functional unit allocation, storage allocation and interconnection allocation. This paper models the allocation problem as cluster analysis and applies a new algorithm, neighbor state transition (NST) algorithm, for cluster optimization. It is proved that the algorithm produces an asymptotically global optimal solution with the upper bound on the cost function (1 + O(1/n)2-ε)F*, When F" is the cost of the optimum solution, n is the problem size and e is a positive parameter arbitrarily close to zero. The numerical examples show that the NST algorithm produces better results compared to the other known methods.

Failure mechanism of a large-scale composite deposits caused by the water level increases

The failure of slope caused by variations in water levels on both banks of reservoirs is common.Reservoir landslides greatly threaten the safety of reservoir area.Taking large-scale composite deposits located on the Lancang River in Southwest China as a study case,the origin of the deposits was analyzed based on the field investigation and a multi-material model was established in the physical model test.Combined with numerical simulation,the failure mechanism of the composite deposits during reservoir water level variations was studied.The results indicate that the deformation of the large-scale composite deposits is a staged sliding mode during the impoundment process.The first slip deformation is greatly affected by the buoyancy weight-reducing effect,and the permeability of soil and variation in the water level are the factors controlling slope deformation initiation.The high water sensitivity and low permeability of fine grained soil play an important role in the re-deformation of deposits slope.During the impoundment process,the deformation trend of the deposit slope is decreasing,and vertical consolidation of soil and increasing hydrostatic pressure on the slope surface are the main reasons for deformation attenuation.It is considered that the probability of large-scale sliding of the deposits during the impoundment period is low.But the damage caused by local bank collapse of the deposit slope still needs attention.The results of this paper will further improve our understanding of the failure mechanism of composite deposits caused by water level increases and provide guidance for the construction of hydropower stations.

Resource allocation based on fairness and QoS provisioning for OFDMA-WLAN system

To satisfy different service requirements of multiple users in the orthogo nal frequency division multiple access wireless local area network OFDMA-WLAN system downlink transmission a resource allocation algorithm based on fairness and quality of service QoS provisioning is proposed. Different QoS requirements are converted into different rate requirements to calculate the QoSs atisfaction level.The optimization object is revised as a fairness-driven resource optimization function to provide fairness. The complex resource allocation problem is divided into channel allocation and power assignment sub-problems. The sub-problems are solved by the bipartite graph matching and water-filling based method.Compared with other algorithms the proposed algorithm sacrifices less data rate for higher fairnes and QoS satisfaction.The sim ulation results show that the proposed algorithm is capableo fp rovi ding QoS and fairness and performs better in a tradeoff among QoS fairness and data rate.

Experimental study on hysteretic behavior of prestressed truss concrete composite beams

This paper describes an experimental study of the hysteretic behavior of prestressed truss concrete composite beams （PTCCBs） under cyclic loading. Five beam models were designed and tested, in which the testing parameters include the global reinforcement index β0, the prestress level 2 and the ratio of stirrup ρsv in the potential plastic hinge zones. Based on the test results, the failure mode and hysteretic behavior of the tested models are obtained. In addition, the P-△ and sectional M-φ hysteretic models for the PTCCBs at the midspan are established. The P-△ hysteretic model shows good agreement with the test results.

Effects of Extracorporeal Shockwave Therapy and Hand Massage on Body Composition and Serum Lipids According to Serum Cholesterol Level in Korean Women

Obesity, particularly abdominal obesity, increases the risk of cardiovascular disease (CVD). This study investigates the effects of six-week (twice a week, 12 sessions total) extracorporeal shockwave therapy (SWT) and hand massage therapy (HT) on body composition and serum lipids in overweight and obese Korean women aged between 35 and 59, according to their serum cholesterol level (≥200 mg/dL versus <200 mg/dL). After the program, weights decreased significantly in both the HT Group and SWT Group (p < 0.05);weights of those with cholesterol < 200 mg/dL significantly decreased in the HT Group (p = 0.038), while weights of those with cholesterol ≥ 200 mg/dL significantly decreased in the SWT Group (p = 0.001). BMIs decreased significantly in both the HT Group and the SWT Group (p < 0.05);BMIs of those with cholesterol < 200 mg/dL significantly decreased in the HT Group (p = 0.018), while BMIs of those with cholesterol ≥ 200 mg/dL significantly decreased in the SWT Group (p = 0.001). The body fat percentage of subjects significantly decreased only in the SWT Group (p = 0.027);the waist-hip ratio significantly decreased only in HT Group (p = 0.034). Serum cholesterol levels significantly decreased in those with cholesterol < 200 mg/dL in the HT Group (p < 0.05) and those with cholesterol ≥ 200 mg/dL in SWT Group (p = 0.055). Triglyceride significantly decreased in both those with cholesterol < 200 mg/dL and those with cholesterol ≥ 200 mg/dL, but did not significantly decrease in either subgroup of the HT Group. The study results suggest that SWT is effective in improving body measurements and serum lipids in those with cholesterol ≥ 200 mg/dL, while HT therapy is effective in those with cholesterol < 200 mg/dL. In conclusion, SWT and HT improved abdominal obesity by reducing body weight and waist circumference and helped improving serum lip index, suggesting the benefit for managing body measurements and serum lipids of overweight and obese individuals.

Seismic fragility analysis of composite frame structure based on performance

Steel-concrete composite structures that share the advantages of both steel structure and concrete structure have been developed rapidly and used widely. It has been a popular structure in high-rise buildings in recent years. Although more and more composite structures have been used in earthquake area, only a few literatures about fragility analysis of this type of structure are available. In this paper, a fragility analysis method based on performance is proposed, in which both the uncertainty due to variability in structures and ground motion are considered. Seismic fragility analysis is performed for a 15-story composite beam-concrete-filled square steel tube column frame by the proposed method. The top-drift-angle and the story-drift-angle are used as quantitative indexes to define the four different performance levels. Then seismic demand probability analysis is carried out and fragility curves are derived to assess the seismic performance of this type of structure.

Effects of Dietary Energy Level and Source on Blood Metabolites,Hormone Secretion and Follicular Fluid Composition in Gilts

The objective of the study was to investigate the effects of dietary energy levels and sources on the blood metabolites,hormone secretion and the composition of follicular fluid in gilts.Fifty-four gilts with initial body weight of(59±4.2) kg were randomly allotted to six treatments.Treatments were low, normal,and high energy feeding levels,which were 87.5%,100%and 112.5%of recommendatory energy requirements by NRC(1998),respectively,and dietary energy sources(starch or fat).Blood samples and follicular fluids were collected on D18 and D19 of the second estrous cycle.The results showed that plasma concentrations of triglycerides and total cholesterol were higher in the fat group than that in the starch group(P【0.05),but those of glucose were similar between the two energy sources(P】0.05);dietary energy level exerted no effect on blood metabolites concentration(P】0.05).Gilts fed the high energy diet had a higher area under curve of plasma insulin(Insulin AUC),insulin-like growth factor-Ⅰ(IGF-Ⅰ) and leptin than did gilts fed the lower energy diet(P【0.05),but there was no significant difference between fat versus starch(P】0.05).Luteinizing hormone(LH) pulses were higher in gilts fed high energy rather than that in low energy diets(P】0.05),plasma concentration of estradiol(E2) was higher in the fat group than that in the starch group(P【0.05).The number of large follicles(diameter≥4 mm) and concentrations of IGF-Ⅰand E2 in follicular fluid were increasing significant as the level of energy increased(P【0.05),but the numbers of large follicles and follicular fluid composition were not affected by the source of dietary energy(P】0.05).The results indicate that gilts fed high energy diets had elevated plasma concentrations of metabolic hormones,IGF-Ⅰand LH secretion,and increased follicular fluid concentrations of IGF-Ⅰ,E2 and numbers of large follicles;gilts fed the dietary fat had a higher plasma concentration of cholesterol and E2.

Adaptive Energy Efficient Power Allocation Scheme for DAS with Multiple Receive Antennas

Energy efficiency(EE)of downlink distributed antenna system(DAS)with multiple receive antennas is investigated over composite Rayleigh fading channel that takes the path loss and lognormal shadow fading into account.Our aim is to maximize EE which is defined as the ratio of the transmission rate to the total consumed power under the constraints of the maximum transmit power of each remote antenna.According to the definition of EE,the optimized objective function is formulated with the help of Lagrangian method.By using the Karush-KuhnTucker(KKT)conditions and numerical calculation,considering both the static and dynamic circuit power consumptions,an adaptive energy efficient power allocation(PA)scheme is derived.This scheme is different from the conventional iterative PA schemes based on EE maximization since it can provide closed-form expression of PA coefficients.Moreover,it can obtain the EE performance close to the conventional iterative scheme and exhaustive search method while reducing the computation complexity greatly.Simulation results verify the effectiveness of the proposed scheme.

Buckling optimization of curvilinear fiber-reinforced composite structures using a parametric level set method

Owing to their excellent performance and large design space,curvilinear fiber-reinforced composite structures have gained considerable attention in engineering fields such as aerospace and automobile.In addition to the stiffness and strength of such structures,their stability also needs to be taken into account in the design.This study proposes a level-set-based optimization framework for maximizing the buckling load of curvilinear fiber-reinforced composite structures.In the proposed method,the contours of the level set function are used to represent fiber paths.For a composite laminate with a certain number of layers,one level set function is defined by radial basis functions and expansion coefficients for each layer.Furthermore,the fiber angle at an arbitrary point is the tangent orientation of the contour through this point.In the finite element of buckling,the stiffness and geometry matrices of an element are related to the fiber angle at the element centroid.This study considers the parallelism constraint for fiber paths.With the sensitivity calculation of the objective and constraint functions,the method of moving asymptotes is utilized to iteratively update all the expansion coefficients regarded as design variables.Two numerical examples under different boundary conditions are given to validate the proposed approach.Results show that the optimized curved fiber paths tend to be parallel and equidistant regardless of whether the composite laminates contain holes or not.Meanwhile,the buckling resistance of the final design is significantly improved.

基于water-level调整的认知无线电传输速率计算算法

在瑞利衰落模型下,根据认知用户的效用函数,来解决认知无线电中的信道规划问题,进而得到认知用户的传输速率。当认知用户传输功率和比特误码率受限时,其最终效用仅与water-level有关,因此文中提出了一种基于water-level调整的功率分配及算法,实现了认知无线电中载波及功率的合理分配,并得到了认知用户的传输速率.理论与仿真分析表明:该算法具有较低的运算复杂度和接近于最优算法的认知用户效用;调整因子仅与算法的收敛速度有关,而与用户总效用及信道的分配结果无关.

优化县域义务教育资源配置的实践审视与路径

我国义务教育实行“以县为主”的管理体制。随着学龄人口的变化、新型城镇化的发展、地方财政紧缩以及义务教育优质均衡发展的要求,县域义务教育学校出现“城挤、乡弱、村空”的现象,义务教育资源配置面临新的挑战。各地在优化县域义务教育资源配置时,注重党政协同推进,强化办学标准引领,完善配套服务与加大投入力度,教育资源整合有力促进了义务教育优质均衡发展。同时,建立同人口变化相协调的基本公共教育服务供给机制,需要理性看待和因地制宜推进新一轮乡村学校布局调整,加强顶层设计,完善县域义务教育学校办学标准;加大教育投入,改进县域义务教育经费保障机制;统筹师资配置,促进县域义务教育强校提质扩优;盘活闲置资源,出台闲置校舍处置指导意见。

多级缓存的内存分配器MCMalloc应用研究

文章研究和分析了通用内存分配器PTMAlloc2和TCMalloc的特点,通过借鉴现有通用内存分配器的优秀设计思想,提出了一种基于多级缓存的内存分配器MCMalloc。通过在不同层级上分配缓存,极大地减少锁的使用,降低锁竞争,提升了高并发系统的内存分配性能,并且支持不同层级之间的内存回收和同层级之间的内存迁移,避免内存分配效率恶化,提升了内存分配器的稳定性。通过TCMalloc官网数据和MCMalloc实验结果分别与PTMalloc2对比分析,在高并发场景下MCMalloc比TCMalloc能更好地改善了内存操作性能。

Caries-related factors and bacterial composition of supragingival plaques in caries free and caries active Algerian adults

Objective: To compare oral hygiene practices, education and social background, food intake and oral malodor of Algerian adults suffering from dental caries with normal controls, and to determine and compare the bacterial composition of the supragingival plaques from the above-mentioned groups.Methods: Participants completed a questionnaire and were clinically examined for dental caries using decayed, missing and filled teeth index according to the criteria laid down by the World Health Organization. Supragingival plaque samples were collected from 50 caries-free adults(CF) and 50 caries-active adults(CA). Standard procedures of culture and identification of aerobic and anaerobic bacteria were used. Data were analyzed using Chi-square test.Results: A total of 117 bacterial strains were isolated from supragingival plaques in CF group subjects, 76(64.96%) of them belonged to 9 aerobic genera, and 41(35.04%) to 9anaerobic genera(P < 0.05). While in the second group, 199 strains were isolated, 119(59.80%) of the strains belonged to 10 aerobic genera and 80(40.20%) to 10 anaerobic bacteria(P < 0.05). Streptococcus mutans, Enterococcus faecium, Aerococcus viridans,Actinomyces meyeri, Lactobacillus acidophilus and Eubacterium limosum showed a significantly higher prevalence in the CA group(P < 0.05). The findings revealed that CA group had a high sugar intake(80%). A significantly higher frequency of tooth brushing(P < 0.000) and a significantly less self-reported oral malodor(P < 0.000) and tooth pain(P < 0.000) were found in CF group, while there was no association of socioeconomic levels and intake of meal snacks with dental caries.Conclusions: This study confirms the association of some aciduric bacteria with caries formation, and a direct association of sugar intake and cultural level with dental caries.Furthermore, oral hygiene practices minimize the prevalence of tooth decay.

Day-ahead allocation of operation reserve in composite power systems with large-scale centralized wind farms

This paper focuses on the day-ahead allocation of operation reserve considering wind power prediction error and network transmission constraints in a composite power system.A two-level model that solves the allocation problem is presented.The upper model allocates operation reserve among subsystems from the economic point of view.In the upper model,transmission constraints of tielines are formulated to represent limited reserve support from the neighboring system due to wind power fluctuation.The lower model evaluates the system on the reserve schedule from the reliability point of view.In the lower model,the reliability evaluation of composite power system is performed by using Monte Carlo simulation in a multi-area system.Wind power prediction errors and tieline constraints are incorporated.The reserve requirements in the upper model are iteratively adjusted by the resulting reliability indices from the lowermodel.Thus,the reserve allocation is gradually optimized until the system achieves the balance between reliability and economy.A modified two-area reliability test system (RTS) is analyzed to demonstrate the validity of the method.

Effects of the Amplitude and Frequency of Salinity Fluctuation on the Body Composition and Energy Budget of Juvenile Tongue Sole(Cynoglossus semilaevis)

Effects of the amplitude(± 2, ± 4, ± 6, and ± 8) and frequency(2, 4, and 8 d) of salinity fluctuation on the body composition and energy budget of juvenile tongue sole(Cynoglossus semilaevis) were investigated in a 64-d experiment. Results showed that the amplitude and frequency of salinity fluctuation had significant interaction and both substantially affected the final weight and specific growth rate of juvenile tongue sole. The tongue sole exhibited better growth in treatments with moderate amplitude and frequency of salinity fluctuation(amplitude ± 4–6; frequency 4–8 d) than in other treatments and the control. In terms of energy budget, salinity fluctuation strongly affected the proportions of energy components, including those deposited for growth and lost in respiration, feces, and excretion. Moderately amplitude and frequency of salinity fluctuationg that favored the growth of tongue sole partitioned more energy for growth and less energy for metabolism than the constant and other amplitude and frequency of salinity fluctuation. Average energy budget for tongue sole at moderately fluctuating salinity was determined to be 100C(food) = 30.92G(growth) + 10.30F(feces) + 6.77U(excretion) + 52.01R(respiration). Energetic advantage at moderately fluctuating salinity, including increased energy intake, high assimilation efficiency, reduced metabolism expenditure, and more energy partitioned into growth, might account for the enhancement of tongue sole growth. Commercial farmers are recommended to rear juvenile tongue sole with moderate salinity fluctuations for better growth performance of this species.

Food web structure and trophic levels in a saltwater pond sea cucumber and prawn polyculture system

The food sources of aquacultured Apostichopus japonicus and the trophic levels of organisms in a sea cucumber（A. japonicus） and prawn（Penaeus japonica） polyculture system in a saltwater pond in Zhuanghe, Liaoning Province were examined using carbon and nitrogen stable isotopes. Across organisms, δ13C ranged from（–25.47±0.20）‰ to（–16.48±0.17）‰（mean±SD）, and δ15N ranged from（4.23±0.49）‰ to（12.44±0.09）‰. The δ13C and δ15N contents of A. japonicus, P. japonica and Fenneropenaeus chinensis were comparatively higher than those of other organisms. Values of δ13C and δ15N revealed that P. japonica, Hemigrapsus sanguineus and Neomysis japonica comprised the largest component of the diet of A. japonicus. The mean trophic level of the organisms in this saltwater pond polyculture system was（2.75±0.08）. P. japonica, A. japonicus, F. chinensis,Synechogobius hasta and Neomysis japonica were in the 3rd trophic level（2–3）; jellyfish, H. sanguineus and zooplankton were in the 2nd trophic level（1–2）; and Enteromorpha prolifera, benthic microalgae, periphyton and suspended matter primarily consisting of phytoplankton, bacteria and humus were in the primary trophic level（0–1）.

Experimental Investigation of Two-Dimensional Shock Initiation Process of Cast Composition B

A two-streak high-speed photography measuring system is designed, which can successfully record the reactive shock front and the reaction profile within the run distance of shock initiation under two-dimensional shock initiation. The strong reaction delay time and the shape of reaction shock front are determined in the cast composition B (RDX/TNT/60/40). A low level reaction zone has been found and analyzed..

Adaptive Runtime Monitoring of Service Level Agreement Violations in Cloud Computing

The cloud service level agreement(SLA)manage the relationship between service providers and consumers in cloud computing.SLA is an integral and critical part of modern era IT vendors and communication contracts.Due to low cost and flexibility more and more consumers delegate their tasks to cloud providers,the SLA emerges as a key aspect between the consumers and providers.Continuous monitoring of Quality of Service(QoS)attributes is required to implement SLAs because of the complex nature of cloud communication.Many other factors,such as user reliability,satisfaction,and penalty on violations are also taken into account.Currently,there is no such policy of cloud SLA monitoring to minimize SLA violations.In this work,we have proposed a cloud SLA monitoring policy by dividing a monitoring session into two parts,for critical and non-critical parameters.The critical and non-critical parameters will be decided on the interest of the consumer during SLA negotiation.This will help to shape a new comprehensive SLA based Proactive Resource Allocation Approach(RPAA)which will monitor SLA at runtime,analyze the SLA parameters and try to find the possibility of SLA violations.We also have implemented an adaptive system for allocating cloud IT resources based on SLA violations and detection.We have defined two main components of SLA-PRAA i.e.,(a)Handler and(b)Accounting and Billing Manager.We have also described the function of both components through algorithms.The experimental results validate the performance of our proposed method in comparison with state-of-the-art cloud SLA policies.