Peer Pressure and Family Smoking Habits Influence Smoking Uptake in Teenage Boys Attending School: Multilevel Modeling of Survey Data

Introduction: Among young teens, about one in five smokes worldwide. Adolescents spend a considerable amount of their time in school, and the school environment is therefore important for child health practices and outcomes. Objectives: We aimed to investigate the impact on smoking behavior of the school environment and the personal characteristics of male teenage students attending schools in Pakistan, taking into account the survey sampling structure. Methods: A two-stage cluster sampling with stratification was employed, and we interviewed 772 male secondary school students. We adopted random effect and generalizing estimating equation models. Results: Peer pressure in particular had a strong influence on adolescents smoking;those whose friends smoked were up to 6 times more likely to smoke. Family smoking was also significantly associated with adolescents smoking, but those students whose mother was educated were 50% less likely to smoke. The fitted random effect model indicated that the between school variability was significant (p-value < 0.01), indicating differences in smoking habits between schools. A random coefficient model showed that variability among schools was not significantly different for public and private schools. Conclusion: Public health campaigns for smoking cessation should target not only the individual but also the families of adolescents attending schools.

A New Perspective to Evaluate Doppler Vascular Impedance in Hypertensive Disorders Complicating Pregnancy: Multilevel Modeling Established in a Case Control Study

Background: There have been researches on the evaluation of Doppler vascular impedance in hypertensive disorders complicating pregnancy (HDCP). With respect to the method of analysis used and the conclusions drawn in previous studies, different vessels were usually viewed separately and independently. This study was designed to evaluate Doppler vascular impedance changes in HDCP from a new perspective, with original thought and insight into an ordinary issue. Methods: 273 pregnant women (110 hypertensive pregnancies and 163 normotensive pregnancies) were randomly included in a grouping case-control study conducted from February 10, 2011 to April 30, 2013. All women in the study underwent Doppler measurements of six different vessels including the umbilical artery, the uterine arteries, the placental bed spiral artery, the fetal middle cerebral artery and the fetal renal artery. Doppler vascular impedance was presented as pulsatility index (PI), resistance index (RI), and systolic and diastolic ratio (S/D). Doppler changes in the hypertensive and normotensive groups were assessed by the multilevel modeling approach with univariate and multivariate-adjusted analyses. Results: According to multilevel modeling approach with multivariate-adjusted analysis, a relatively average evaluation on Doppler vascular impedance was provided. Hypertension was significantly associated with positive effects on PI, RI and S/D values (coefficients were 0.10, 0.03 and 0.08, respectively;95% CIs were 0.06 - 0.14, 0.02 - 0.04 and 0.04 - 0.11, respectively;P values were all less than 0.001) in comparison with normotensive group. Conclusion: According to an overall evaluation, Doppler vascular impedance in hypertensive disorders complicating pregnancy was higher than in normotensive pregnancy. The novel thought and approach applied in this research may bring about inspirations for better understanding and assessment of the disease.

Applying Multivariate Multilevel Models to Explore Arable Land Quality in Sub-Saharan Africa: A Case Study in Kenya

Controversy exists on the magnitude and variability of farm nutrient balances and quality of arable land in sub-Saharan Africa with Kenya among those affected negatively. This study investigates quality of arable land by fitting multivariate multilevel model to farm nutrient balance data collected from five agro-climatic zones of Kenya (arable lands). Objectives of the study were to investigate the magnitude and variability of Nitrogen, Phosphorus and Potassium (NPK) farm nutrient balances in arable lands of Kenya, study effects of agro-climatic zones on nutrient balances and to determine effects of household resource endowments on NPK nutrient balances. The study concludes that agro-climatic zones differ with respect to farm nutrient balances;that livestock resource endowments and hired labour have positive effects on the magnitude and direction of farm nutrient balances;and that household ownership of large capital resources do not guarantee a positive effect on farm nutrient balances. The study recommends integration of sound livestock practices and application of agro-climatic zone differentiated interventions in future strategies for addressing farm nutrient balances and arable land quality, and the use of large sample sizes and relevant factors/covariates in future analysis to shed additional insights on farm nutrient balances and on how arable land quality can be improved.

Correlates of Parental Choice of Child Discipline Methods in Ghana: A Multilevel Modeling Approach

This study applied multilevel modeling to investigate the impact of observed predictors and different levels or groups that households belong, on parents’ choice of discipline methods using data from 8156 households derived from a nationwide survey by the Ghana Statistical Service (GSS) in 2011. The aim of the study is to provide in-depth information on why parents choose particular discipline methods as corrective measures to reduce unwanted child behaviour in the present and to increase desirable ones in the future. The results of the study show that, religion and age-group of household heads have significant effect on household’s likelihood to choose physical discipline methods whereas the wealth index of a household and ethnicity of the household head, have significant effect on households’ likelihood to choose non-physical and psychological aggression methods. The results further show significant contextual effect on the differences in choices of parents at the household and regional levels. The choice of physical discipline methods by parents was consistent across households and regional levels unlike non-physical and psychological aggression methods whose application varied across the regions. Households in the Northern, Eastern and Volta regions mostly chose to apply physical discipline methods whereas in the Upper West, Western and Northern regions the most chosen discipline methods were non-physical discipline methods. Psychological aggression discipline methods were predominantly applied in the Upper East, Central and Northern regions of the country.

Human induced dryland degradation in Ordos Plateau,China,revealed by multilevel statistical modeling of normalized difference vegetation index and rainfall time-series

Land degradation causes serious environmental problems in many regions of the world, and although it can be effectively assessed and monitored using a time series of rainfall and a normalized difference vegetation index （NDVI） from remotely-sensed imagery, dividing human-induced land degradation from vegetation dynamics due to climate change is not a trivial task. This paper presented a multilevel statistical modeling of the NDVI-rainfall relationship to detect human-induced land degradation at local and landscape scales in the Ordos Plateau of Inner Mongolia, China, and recognized that anthropogenic activities result in either positive （land restoration and re-vegetation） or negative （degradation） trends. Linear regressions were used to assess the accuracy of the multi- level statistical model. The results show that： （1） land restoration was the dominant process in the Ordos Plateau between 1998 and 2012; （2） the effect of the statistical removal of precipitation revealed areas of human-induced land degradation and improvement, the latter reflecting successful restoration projects and changes in land man- agement in many parts of the Ordos; （3） compared to a simple linear regression, multilevel statistical modeling could be used to analyze the relationship between the NDVI and rainfall and improve the accuracy of detecting the effect of human activities. Additional factors should be included when analyzing the NDVI-rainfall relationship and detecting human-induced loss of vegetation cover in drylands to improve the accuracy of the approach and elimi- nate some observed non-significant residual trends.

Multilevel security model for ad hoc networks

Modern battlefield doctrine is based on mobility, flexibility, and rapid response to changing situations. As is well known, mobile ad hoc network systems are among the best utilities for battlefield activity. Although much research has been done on secure routing, security issues have largely been ignored in applying mobile ad hoc network theory to computer technology. An ad hoc network is usually assumed to be homogeneous, which is an irrational assumption for armies. It is clear that soldiers, commanders, and commanders-in-chief should have different security levels and computation powers as they have access to asymmetric resources. Imitating basic military rank levels in battlefield situations, how multilevel security can be introduced into ad hoc networks is indicated, thereby controlling restricted classified information flows among nodes that have different security levels.

Study of visualized simulation and analysis of nuclear fuel cycle system based on multilevel flow model

Complex energy and environment system, especially nuclear fuel cycle system recently raised socialconcerns about the issues of economic competitiveness, environmental effect and nuclear proliferation. Only underthe condition that those conflicting issues are gotten a consensus between stakeholders with different knowledgebackground, can nuclear power industry be continuingly developed. In this paper, a new analysis platform has beendeveloped to help stakeholders to recognize and analyze various socio-technical issues in the nuclear fuel cycle systembased on the functional modeling method named Multilevel Flow Models (MFM) according to the cognition theoryof human being. Its character is that MFM models define a set of mass, energy and information flow structures onmultiple levels of abstraction to describe the functional structure of a process system and its graphical symbol representationand the means-end and part-whole hierarchical flow structure to make the represented process easy to beunderstood. Based upon this methodology, a micro-process and a macro-process of nuclear fuel cycle system wereselected to be simulated and some analysis processes such as economics analysis, environmental analysis and energybalance analysis related to those flows were also integrated to help stakeholders to understand the process of decision-making with the introduction of some new functions for the improved Multilevel Flow Models Studio, and finallythe simple simulation such as spent fuel management process simulation and money flow of nuclear fuel cycleand its levelised cost analysis will be represented as feasible examples.

SPICE modeling of memristors with multilevel resistance states

With CMOS technologies approaching the scaling ceiling, novel memory technologies have thrived in recent years, among which the memristor is a rather promising candidate for future resistive memory （RRAM）. Memristor＇s potential to store multiple bits of information as different resistance levels allows its application in multilevel cell （MCL） tech- nology, which can significantly increase the memory capacity. However, most existing memristor models are built for binary or continuous memristance switching. In this paper, we propose the simulation program with integrated circuits emphasis （SPICE） modeling of charge-controlled and flux-controlled memristors with multilevel resistance states based on the memristance versus state map. In our model, the memristance switches abruptly between neighboring resistance states. The proposed model allows users to easily set the number of the resistance levels as parameters, and provides the predictability of resistance switching time if the input current/voltage waveform is given. The functionality of our models has been validated in HSPICE. The models can be used in multilevel RRAM modeling as well as in artificial neural network simulations.

A Regional Spectral Nested Multilevel Primitive Equation Model

By means of vertical normal modes a regional nested multilevel primitive equation model can be reduced to several sets of shallow water equations characterized by various equivalent depths. Therefore, time integration of the model in spectral form can be performed in the manner similar to those used in the spectral nested shallow water equation model case.

Support Operator’s Fault Diagnosis of Complex Plant Systemthrough Multilevel Flow Model and Ecological Interface Design

The paper describes a new human-interface system design method by combining the conception of Multilevel Flow Model and Ecological Interface Design to support operators’ fault diagnosis in the complex plant system. Modern man-made systems are always achieving many complex automatic and intelligent tasks so that they are becoming more and more complex and can be hardly understood by operators, who should be the primary role in system operating. This situation presents a big challenge to the operating support system that it should present the complex system in a direct and clear way to operators to and make operators understand the internal interaction of the system especially in the abnormal status to ensure the operating safety. The Multilevel Flow Model based on the idea of ”Abstraction Hierarchy”, aiming at decompressing a system by means-end and part-whole way, can be used to represent a complex system in a standard way and perform intelligent operating tasks such as fault diagnosis and process control. Ecological Interface Design, which based on the human cognitive properties, can present the internal interaction of the system in a direct way. This paper combines this two interface design conceptions to achieve two aspects, intelligent fault diagnosis and direct presentation of causal relationship of operating parameters, to support operators’ fault diagnosis in complex plant system. The design method is applied to a PWR power plant in this paper as an application example.

Effect of socio-demographic status on dental caries in pupils by using a multilevel hurdle model

Introduction: Dental caries is the most prevalent chronic disease among schoolchildren. We aimed to investigate the association between dental caries index and socio-demographic status in schoolchildren by using a multilevel hurdle model. Materials and Methods: A cross-sectional epidemiological study was carried out on 906 primary school pupils in Kerman, Iran in 2012. The subjects were selected through a stratified cluster random sampling. At first, the whole target area was stratified according to two geographic areas, the north and south area. Then each area was stratified according to gender. In the next step, several schools were considered as clusters, which were selected randomly in each geographic area and gender strata. All the schoolchildren in these schools were included in this study as samples. Twelve-year-old pupils were examined for dental caries. The dependent variable in this study was the dmft/DMFT index. Eight variables, including socio-demographic information, were collected. Multilevel negative binomial hurdle model was employed for data analysis. Results: The prevalence of caries-free pupils was 30.1% and the mean dmft/DMFT was 3.6 ± 2.2. Negative binomial part of the adjusted model showed that the dmft/DMFT adjusted rate for females was 1.36 (95% CI: 1.10-1.79) times higher than males. Also, the dmft/DMFT adjusted rate for overweight pupils was 0.86 (95% CI: 0.74-0.98) times lower than those with normal weight. Logistic part of the adjusted model showed that the posibility of caries-free state in overweight pupils was 1.95 (95% CI: 1.22-3.11) times higher than those with normal weight. In addition, pupils whose fathers and mothers were workers and housewives, respectively, and those with a high maternal age were at a greater risk for caries experience than others (p < 0.05). Conclusion: BMI, gender, parent’s job and mother’s age at delivery were factors effecting on dental caries in schoolchildren. These pupils need more attention to dental care.

Multiple-Attribute and Multilevel Synthetic Evaluation Model and Its Application

On the basis of analyzing the flaws of present multiple-attribute and multilevel evaluation methods, concerning the problem of characteristics of the multiple-attribute and multilevel system s appraisal and the particular emphasis on the respective attributes in the evaluation process, as well as its relevance to the environment, an optimal attribute system is proposed, and the multiplicative analytic hierarchy process (MAHP) is used to obtain subjective weight coefficients and the objective weight coefficient evaluating method is given. The deviation between the index value of each level and the values of the same index of other levels are formulated, and an optimal model is gained, thus establishing the weight coefficients of the whole optimal attribute system. Furthermore, the detailed implementation procedure of this method is introduced. Besides, favorable results have been gained by applying the model to the practical problems of economic evaluation.

Effects of Differential Item Discriminations between Individual-Level and Cluster-Level under the Multilevel Item Response Theory Model

This study attempted to interpret differential item discriminations between individual and cluster levels by focusing on patterns and magnitudes of item discriminations under 2PL multilevel IRT model through a set of variety simulation conditions. The consistency between the mean of individual-level ability estimates and cluster-level ability estimates was evaluated by the correlations between them. As a result, it was found that they were highly correlated if the patterns of item discriminations were the same for both individual and cluster levels. The magnitudes of item discriminations themselves did not affect much on correlations, as far as the patterns were the same at the two levels. However, it was found that the correlation became lower when the patterns of item discriminations were different between the individual and cluster levels. Also, it was revealed that the mean of the estimated individual-level abilities would not be necessarily a good representation of the cluster-level ability, if the patterns were different at the two levels.

A Visual Integrated Analysis Platform for Nuclear Fuel Cycle System Based on Multilevel Flow Model

Complex Nuclear Fuel Cycle (NFC) system faces many socio-technical issues that need to obtain the consensus between stakeholders of different knowledge background. In this paper, a visualized analysis platform based on graphical functional modeling method, Multilevel Flow Model (MFM), is proposed to help those stakeholders to recognize and analyze various socio-technical issues in NFC system. Some new functions, such as “Reaction Function", “Switch Function" and “Conversion Function", are introduced to fulfill new simulation tasks for NFC system. Based upon this methodology, a micro-process and a macro-process of NFC system are simulated and meanwhile some key analysis variables, such as CO2 emission and cost flow, required by some analysis methods are deducted and displayed in the platform. And finally a sample simulation analysis is conducted based on MFM.

多层次领导力发展模型的构建及其有效性检验——基于扎根理论的探索性研究

领导力发展对企业人力资源开发和领导者培养至关重要,而关于领导力发展的具体内容和如何验证发展结果的有效性,一直存有争议。采用扎根理论的研究方法,对正在进行领导力发展计划的A企业进行深度访谈和现场研究,构建了一个多层次视角的领导力发展模型。该模型基于发展自我、发展团队、发展组织的多层次视角,提出了领导力的发展内容包括做人、做事、发展下属、凝聚团队、组织管理、业绩管理六个核心要素。进一步将该模型与“方向-协作-承诺”模型(DAC模型)做对比分析,研究结果表明“发展自我”激发承诺,“发展团队”产生方向、协作和承诺,“发展组织”促进方向和协作,从而验证了该领导力发展模型的有效性。

治理嵌入与经济增长要素效率——基于多层统计模型的分析

文章基于中国省际数据,对经济增长要素效率的治理嵌入影响进行了实证分析,结果表明:省际资本效率、劳动效率、人力资本效率和技术创新效率存在异质性;行政、市场和社会三种治理方式及其交互项通过显著影响基本驱动要素的效率间接影响经济增长。因此,在分析经济增长时,既要考虑基本驱动因素,也要考虑治理嵌入性因素对影响要素效率的作用,同时要根据各省之间影响的异质性和不同时期的趋势,围绕效率的提升设计政策体系,以实现高质量的经济增长。

超导磁储能装置提高柔性直流配电系统稳定性的研究

柔性直流配电系统中定功率控制的换流器具有恒功率负载特性,会降低系统阻尼,对系统的稳定性产生不利影响。针对该问题,在直流配电系统中加入超导磁储能SMES(superconducting magnetic energy storage)装置来提高系统的稳定性。推导了柔性直流配电系统的反馈控制模型,采用频域分析法研究了换流器恒功率负载特性对系统稳定性的影响,并结合数学模型和频域分析,指出SMES装置能够为电网提供正阻尼,增大了系统开环传递函数在剪切频率处的相位裕度,从而改善了系统稳定性。为防止超导磁体两端电压过高,SMES装置与直流配电网连接的DC/DC换流器需具备一定的电压调节性能,因此研究了采用模块化多电平DC/DC换流器DC-MMC(modular multilevel DC/DC converter)的SMES装置,通过调节子模块个数灵活设置换流器电压变比,在实现换流器能量双向流动的同时控制超导磁体两端电压,以保护储能装置。最后通过时域仿真波形验证了采用DC-MMC的SMES装置在提高柔性直流配电系统稳定性方面的可行性和有效性。

多组分多层级3D打印材料研究进展

多组分多层级3D打印材料(McMl3DPMs)是一种新兴的先进材料,源于多孔材料、复合材料和增材制造的融合。由于增材制造赋予了Mc Ml3DPMs三维架构跨越广泛组分构成和结构类型的能力,Mc Ml3DPMs拥有杰出的机械性能,甚至是通常被认为相互排斥的性能(例如高强度和高韧性)。本文重点介绍为了实现高性能结构用Mc Ml3DPMs所必须解决的科学挑战以及最近研究工作对此做出的努力,将从结构设计、制造过程建模、缺陷表征和性能评价3个方面对相关案例进行回顾。最后,本文指出了当前研究的不足之处,并展望了Mc Ml3DPMs的未来发展,包括讨论了进一步推进这一新兴领域发展的几个可能的研究方向。

青海省两地区12岁儿童龋齿影响因素的多水平分析

目的了解青海省西宁市及海东市12岁儿童口腔健康状况及个体和学校水平上的影响因素,为制定和完善青海省儿童口腔干预政策提供依据。方法利用青海省2016年第四次口腔流行病学调查数据,采用多水平Logistic回归模型对813名12岁儿童口腔状况及影响因素进行分析。结果青海省两地区12岁儿童患龋率为29.90%,女性儿童患龋率(33.33%)高于男性(26.37%),差异有统计学意义(χ^(2)=4.71,P=0.030),农村儿童患龋率(30.49%)高于城市儿童(28.97%),差异无统计学意义(χ^(2)=0.21,P=0.644);儿童的口腔健康状况在学校水平呈现聚集性(σ_(μ)^(2)=0.002,P<0.001)。多水平Logistic回归分析发现,儿童性别为女性是儿童龋齿的危险因素,OR(95%CI)为1.48(1.08,2.02);儿童母亲最高学历为高中及以上是儿童龋齿的保护因素,OR(95%CI)为0.62(0.39,0.93);儿童自我口腔评价为差或者一般是儿童龋齿的危险因素,OR(95%CI)分别为1.94(1.21,3.16)、1.46(1.01,2.14);认为“定期口腔检查非常必要”是不正确或不知道是儿童龋齿的危险因素,OR(95%CI)为1.21(1.12,1.54)。结论青海省西宁市及海东市12岁儿童龋齿形势依旧严峻,应以女性儿童为重点人群,实施有效的口腔综合干预措施。以学校为平台针对性地设置口腔保健课程,定期开展儿童口腔检查及儿童父母的口腔知识宣教,促使儿童树立正确的口腔健康观、养成良好的口腔健康行为,降低儿童患龋率。

置信区间宽度等高线图在线性混合效应模型样本量规划中的应用

线性混合效应模型在分析具有嵌套结构的心理学实验数据时具有明显优势。本文提出了置信区间宽度等高线图用于该模型的样本量规划。通过等高线图,确定同时符合检验力、效应量准确性以及置信区间宽度要求的被试量和试次数。结合关注被试内实验效应和被试变量调节效应的两类典型模型,通过两个模拟研究,采用基于蒙特卡洛模拟方法,探索效应量、随机效应大小和被试变量类型对置信区间宽度等高线图及样本量规划结果的影响。