CO-OFDM系统中基于线性预处理的新相位噪声抑制算法

针对相干光正交频分复用（coherent optical orthogonal frequency division multiplexing,CO-OFDM）系统中相位噪声引起的载波间干扰（inter-carrier interference,ICI）问题,提出了一种基于线性预处理的新判决反馈相位噪声抑制算法。该新算法改进了线性预处理部分,利用循环前缀与OFDM符号固有的相关性,在时域进行简单的线性组合运算,充分利用了OFDM符号中冗余信息。仿真分析表明,在激光器线宽为200 kHz且误码率（bit error rate, BER）为10－4时,与判决反馈相位噪声抑制算法和一次迭代的判决反馈相位噪声抑制算法相比,该新算法BER曲线的信噪比（signal to noise ratio,SNR）分别改善了3 dB和1 dB,有效地降低由ICI引起的错误平层。     

论破窗理论对高校班级管理的启示

班级管理在大学教育中的作用十分重要。从破窗理论出发,明确了班级环境在班级建设与发展中的重要地位,论述了班级中潜抑力量与压抑力量转化的意义,在此基础上进一步提出,要从加强日常管理、形成良性反馈机制、处理好突发事件三个方面预防“破窗现象”,并针对破窗理论的运用提出了建议。     

Social organization, population, and land use

A new approach to investigation of human influences on the environment identifies social organization as an influence independent of population size, affluence, and technology. The framework also identifies population events, such as births, that influence the environment. The authors use longitudinal, multilevel, mixed-method measures of local land use changes, population dynamics, and social organization to test this framework. These tests reveal that changes in social organization are strongly associated with changes in land use independent of measures of population size, affluence, and technology. Also, local birth events shape local land use changes and key proximate determinants of land use change.     

Social change,out-migration,and exit from farming in Nepal

Population and Environment - Though international out-migration is widespread, little evidence exists regarding the consequences for economic change in sending countries, particularly in the...     

Environmental Change and Out-Migration: Evidence from Nepal

Scholars and activists have hypothesized a connection between environmental change and out-migration. In this paper we test this hypothesis using data from Nepal. We operationalize environmental change in terms of declining land cover, rising times required to gather organic inputs, increasing population density, and perceived declines in agricultural productivity. In general, environmental change is more strongly related to short- than long-distance moves. Holding constant the effects of other social and economic variables, we find that local moves are predicted by perceived declines in productivity, declining land cover, and increasing time required to gather firewood. Long-distance moves are predicted by perceived declines in productivity, but the effect is weaker than in the model of short-distance mobility. We also show that effects of environmental change vary by gender and ethnicity, with women being more affected by changes in the time required to gather fodder and men by changes in the time to gather firewood, and high caste Hindus generally being less affect than others by environmental change.     

Community Context,Land Use,and First Birth

This article examines the influence of community context and land use on the monthly odds of first birth in a society in the midst of dramatic fertility transition. The theoretical framework guiding our work predicts that proximity to nonfamily services should delay first births by creating opportunities for competing nonfamily activities and spreading new ideas that change expectations about family life. On the other hand, living in agricultural settings that provide opportunities for higher returns to child labor should speed first births. We use a longitudinal, multilevel, mixed‐method data from the Nepalese Himalayas to test these predictions. The empirical results reveal that nonfamily services during childhood and during early adulthood both have important independent influences on the odds of first birth. Also, as predicted, a high density of agricultural land use affects the odds of first births in the opposite direction, speeding first births. This clear pattern of contrasting effects provides important new evidence of the contextual dynamics that produce watershed changes in postmarital birth timing.     

Farming Systems and Rural Out‐Migration in Nang Rong,Thailand, and Chitwan Valley,Nepal

Using data from two postfrontier rural settings, Nang Rong, Thailand (N = 2,538), and Chitwan Valley, Nepal (N = 876), this article examines agricultural push factors determining the out‐migration of young people age 15 to 19. We focus on different dimensions of migration, including distance and duration. Our study examines a wide array of agricultural determinants, each with its own potential effect on migration. These determinants include land tenure, crop portfolios, animal husbandry activities, and use of farm inputs. We link these proximal causes to two underlying mechanisms: risk and amenities. We examine these determinants using separate models across settings. Our results indicate that agricultural factors are significant determinants of migration in both contexts. However, different factors operate in different settings, indicating the importance of contextual variation in explaining the manner in which risks and amenities influence agricultural determinants of migration.     

A Micro-Level Event-Centered Approach to Investigating Armed Conflict and Population Responses

In this article, we construct and test a micro-level event-centered approach to the study of armed conflict and behavioral responses in the general population. Event-centered approaches have been successfully used in the macro-political study of armed conflict but have not yet been adopted in micro-behavioral studies. The micro-level event-centered approach that we advocate here includes decomposition of a conflict into discrete political and violent events, examination of the mechanisms through which they affect behavior, and consideration of differential risks within the population. We focus on two mechanisms: instability and threat of harm. We test this approach empirically in the context of the recent decade-long armed conflict in Nepal, using detailed measurements of conflict-related events and a longitudinal study of first migration, first marriage, and first contraceptive use. Results demonstrate that different conflict-related events independently shaped migration, marriage, and childbearing and that they can simultaneously influence behaviors in opposing directions. We find that violent events increased migration, but political events slowed migration. Both violent and political events increased marriage and contraceptive use net of migration. Overall, this micro-level event-centered approach yields a significant advance for the study of how armed conflict affects civilian behavioral responses.     

Environmental change and out-migration: evidence from Nepal

Scholars and activists have hypothesized a connection between environmental change and out-migration. In this paper, we test this hypothesis using data from Nepal. We operationalize environmental change in terms of declining land cover, rising times required to gather organic inputs, increasing population density, and perceived declines in agricultural productivity. In general, environmental change is more strongly related to short- than long-distance moves. Holding constant the effects of other social and economic variables, we find that local moves are predicted by perceived declines in productivity, declining land cover, and increasing time required to gather firewood. Long-distance moves are predicted by perceived declines in productivity, but the effect is weaker than in the model of short-distance mobility. We also show that effects of environmental change vary by gender and ethnicity, with women being more affected by changes in the time required to gather fodder and men by changes in the time to gather firewood, and high-caste Hindus generally being less affect than others by environmental change.     

Knowledge and beliefs about national development and developmental hierarchies: The viewpoints of ordinary people in thirteen countries

Scholars and policy makers have for centuries constructed and used developmental hierarchies to characterize different countries. The hypotheses motivating this paper are that such social constructions have been circulated internationally, are constructed similarly in various countries, and follow the social constructions of elite international organizations, such as the United Nations. This paper uses data from 15 surveys in 13 diverse countries to study how developmental hierarchies are understood in everyday life. Our research shows that most people have constructions of developmental hierarchies that are similar across countries and are similar to the developmental hierarchies constructed by the United Nations. These findings suggest that developmental hierarchies are widely understood around the world and are widely available to ordinary people as they make decisions about many aspects of life.