1988年中国妇女未避孕率研究

中国进入80年代以后,随着避孕药具生产和供应改善,计划生育手术质量提高,避孕知识宣传不断普及深入,避孕组织工作日臻完善,采用避孕措施的人在已婚育龄妇女中的比例逐步上升到70％左右,从而使中国育龄夫妇的避孕进入到一个新的阶段。然而中国毕竟是一个发展中国家,经济文化还不发达,加上传统观念的影响,还有一部份人想生较多的孩子,不愿意采用或不愿意过早采用避孕措施。本文试图阐明当前中国育龄夫妇不避孕的状况,阐明经济、社会诸因素对未避孕率高低的影响,以便为计划生育部门更有效地提高避孕率,进一步降低生育率、控制人口增长提供依据,为科研部门深入研究未避孕率打下基础。

Risk Assessment of Unmanned Aerial Vehicle Flight Based on Kmeans Clustering Algorithm

To quantify unmanned aerial vehicle(UAV)flight risks in low-altitude airspace,we analyze the factors of UAV flight risks from three aspects:flight conflict,flight environment,and traffic characteristics.The aerial risk index and ground risk index of the UAV are constructed,the index screening model and the UAV flight risk assessment model are established,and a UAV flight risk assessment model based on K-means clustering has been proposed.Meanwhile,numerical simulations show the proposed method can not only evaluate the UAV flight risks effectively,but also provide technical support for UAV risk management and control.

Dual Actions for Born-Infeld and Dp-Brane Theories

Dual actions with respect to U(1) gauge fields for the Born-Infeld and Dp-brane theories are reexamined.Taking into account an additional condition,i.e.a corollary to the field equation of the auxiliary metric,one obtainsan alternative dual action that does not involve the infinite series in the auxiliary metric given by [M.Abou Zeid andC.M.Hull,Phys.Lett.B 428 (1998) 277],but just picks out the first term from the series formally.New effectiveinteractions of the theories are revealed.That is,the new dual action gives rise to an effective interaction in terms ofone interaction term rather than infinitely many terms of different (higher) orders of interactions physically.However,the price paid for eliminating the infinite series is that the new action is not quadratic but highly nonlinear in the Hodgedual of a (p-1)-form field strength.This non-linearity is inevitable under the requirement that the two dual actionsare equivalent.

Dynamic reactive power planning method for CSP-PV hybrid power generation system

Aiming at the faults of some weak nodes in the concentrated solar power-photovoltaic(CSP-PV)hybrid power generation system,it is impossible to restore the transient voltage only relying on the reactive power regulation capability of the system itself.We propose a dynamic reactive power planning method suitable for CSP-PV hybrid power generation system.The method determines the installation node of the dynamic reactive power compensation device and its compensation capacity based on the reactive power adjustment capability of the system itself.The critical fault node is determined by the transient voltage stability recovery index,and the weak node of the system is initially determined.Based on this,the sensitivity index is used to determine the installation node of the dynamic reactive power compensation device.Dynamic reactive power planning optimization model is established with the lowest investment cost of dynamic reactive power compensation device and the improvement of system transient voltage stability.Furthermore,the component of the reactive power compensation node is optimized by particle swarm optimization based on differential evolution(DE-PSO).The simulation results of the example system show that compared with the dynamic position compensation device installation location optimization method,the proposed method can improve the transient voltage stability of the system under the same reactive power compensation cost.

On opportunistic spectrum efficiency in cognitive radio systems

The performance bound of cognitive radio systems is analyzed.We use opportunistic spectrum effi-ciency(OSE)as the performance metric,and point out that the maximum achievable OSE can be used toevaluate the maximum value that the introduction of secondary users can add to the conventional wirelesssystems.Based on assumptions of the PU s traffic model and some reasonable approximations,the ex-pression of OSE is obtained and the maximum achievable OSE is derived by solving an optimization prob-lem.The results are verified by computer simulation.

Effects of Water Quality on the Distribution of Chinese Giant Salamander(Andrias davidianus)in Guizhou Province,China

13 water quality parameters were tested from 38 reaches of 34 counties in Guizhou where Chinese giant salamander(Andrias davidianus) distributed over the past 30 years. Dissolved oxygen and p H were found to be significant determinants of the species distribution in recent years(P<0.05). There was no Chinese giant salamander distribution in the recent five years in rivers with dissolved solids of greater than 415 mg/L, conductivity of greater than 639 us/cm, salinity of greater than 0.31 ppt and total hardness of greater than 150 mg/L. Sensitive to environment, the Chinese giant salamander is an important indicator for environmental quality, so it could be used as one of the environmental indicator. Eutrophication, chemical fertilizer, pesticides and inorganic pollutants may be one of reasons driving wild CGS into extinction.

Measuring IP Performance Metrics on Mobile Network with Heterogeneous Wireless Technologies

The new measurement scheme of IP performance metrics is for the mobile network in heterogeneous wireless network environment. In the proposed scheme, when Mobile Nodes （MNs） inside the mobile network needs to understand the condition of multiple comrmunicatinn paths outside the mobile netwtrk, they can get IP performance metrics, such as delay, jitter, bandwidth, packet loss, etc., irrespective of the preserre or absence of measurement functionality. At the same time, the proposed scheme dees not require the MN to he involved in measuring IP performance metrice. The Multihomed Mobile Router （MMR） with heterogeneons wireless interfaces measures IP performance metrics on behalf of the MNs inside the mobile network. Then, MNs can get measured IP perfonmnce metries from the MMR using L3 messages. The proposed scheme can reduce burden and power consumption of MNs with limited resource and batty power since MNs don＇ t measure IP performance metrics directly. In addition, it can reduce considerably traffic overhead over wireless links on multiple measurement paths since signaling messages and injeeted testing traffic are reduced.

Ranking Quality Management Indicators for Radio Programs

Even though radio broadcasting is one of the most widespread electronic mass media, its management for survival is getting drastic. The competition among incumbent radio stations becomes challenging due to the market change and environmental evolution. Managing program quality is a critical issue to a radio station to sharpen its competitive advantages. Quality management of radio programs is intertwined with complicated factors. In order to identify the primary factors affecting radio program quality as well as explore the impact level these factors bring, this study adopts modified Delphi method and analytic hierarchy process （AHP） to explore the issues. According to the outcomes modified Delphi method, the factors were categorized into four dimensions： operation, coordination, structure, and improvement. Ten sub-dimensions were followed. Each sub-dimension includes six to nineteen indicators for measuring radio program quality. In total, 72 indicators were identified. The AHP result revealed that the most important weight was given to the operation dimension. On the contrary, the least important weight was placed on the improvement dimension. Among the sub-dimensions, the standard procedure and organizational design were rated more important than the rest. The results could provide some facts to radio managers for future management.

Genotoxicity biomarkers in aquatic bioindicators

Pollution of the aquatic environment is an ever-growing problem, as waters are the ultimate sink for the large number of xenobiotics from multiple sources. DNA damaging agents have a significant ecological relevance since they are implicated in many pathological processes and exert effects beyond that of individual being active through following generations. A large number of methods have been applied to evaluate genotoxic damage in different aquatic species. Comet assay, as method for de- tecting DNA alterations, and micronucleus test, as an index of chromosomal damage are the most widely applied and validated methods in field studies. These methods were applied in different vertebrate and invertebrate aquatic species, but only mollusk and fish species have been employed in routine biomonitoring programs. Mussels, due to their widely geographical distribution and the suitability for caging represent the bioindicator of choice in field studies. Mytilus species is the most used marine mussel. The use of fish is limited to specific geographic areas. The present review mainly focuses on the application of comet assay and micronucleus test in mussels. A number of biomonitoring studies in mussels, using comet assay or micronucleus test, revealed exposure to different classes of genotoxic compounds with a good discrimination power. The different evidence from the two as- says, reflects different biological mechanisms for the two genetic endpoints, DNA damage and chromosomal damage, suggesting their combined application in the field. Different endogenous and exogenous factors have been shown to modulate the genotoxic responses in mussels, acting as confounding factors in environmental monitoring. The use of standardized protocol for caging, sampling and genotoxity evaluation is critical in biomonitoring studies. The use of a multimarker approach coupling genotoxicity biomarkers with physiological and biochemical factors allows to have a complete picture of the environmental pollution [Current Zoology 60 （2）： 273-284, 2014].

Multiplicity of closed geodesics on Finsler spheres with irrationally elliptic closed geodesics

If all prime closed geodesics on(S^n, F) with an irreversible Finsler metric F are irrationally elliptic,there exist either exactly 2 [(n+1)/2] or infinitely many distinct closed geodesics. As an application, we show the existence of three distinct closed geodesics on bumpy Finsler(S^3, F) if any prime closed geodesic has non-zero Morse index.