Browsing by Author "Du, Chenguang"
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- Experimental and Statistical Investigation of Reservoir Properties with the Effect of Waterflooding TreatmentLi, Zihao; Du, Chenguang; Tang, Yongqiang; Li, Xiangming (2020-08-25)An oilfield reservoir over long-term operation may have different petrophysical information, which has a significant impact on oilfield maintenance and finance. Successful oilfield enhanced oil recovery benefits a lot from identifying and analyzing the variations of the critical properties after long-term water-flooding treatments. Since the inspection wells drilled within different development periods contain the core samples that have the petrophysical information at that period, it is necessary to collect and test the samples from different periods to investigate the overall tendency of the petrophysical properties. The samples from four inspection wells, which were drilled in four stages since the very beginning of development, were subjected to in-laboratory core analysis methods to illustrate the variation of some critical parameters in the reservoir. The permeability and porosity variation are revealed clearly by the experimental results. The migration and dissolution of clay minerals play a crucial role in the variation of petrophysical information and pore structure. To quantify the variations above, we applied the multiple linear regression model into our investigation. The dependent variable and all of the predictors in the model come from the experimental results. The quantitative results show the closed correlation between different parameters in the formation. With the development stage moving forward, the weight coefficients for different predictors have multiple trends. The experimental and statistical approach provides a novel understanding of the reservoir properties with the effect of waterflooding treatment.
- How Well Can Two-Wave Models Recover the Three-Wave Second Order Latent Model Parameters?Du, Chenguang (Virginia Tech, 2021-06-14)Although previous studies on structural equation modeling (SEM) have indicated that the second-order latent growth model (SOLGM) is a more appropriate approach to longitudinal intervention effects, its application still requires researchers to collect at least three-wave data (e.g. randomized pretest, posttest, and follow-up design). However, in some circumstances, researchers can only collect two-wave data for resource limitations. With only two-wave data, the SOLGM can not be identified and researchers often choose alternative SEM models to fit two-wave data. Recent studies show that the two-wave longitudinal common factor model (2W-LCFM) and latent change score model (2W-LCSM) can perform well for comparing latent change between groups. However, there still lacks empirical evidence about how accurately these two-wave models can estimate the group effects of latent change obtained by three-wave SOLGM (3W-SOLGM). The main purpose of this dissertation, therefore, is trying to examine to what extent the fixed effects of the tree-wave SOLGM can be recovered from the parameter estimates of the two-wave LCFM and LCSM given different simulation conditions. Fundamentally, the supplementary study (study 2) using three-wave LCFM was established to help justify the logistics of different model comparisons in our main study (study 1). The data generating model in both studies is 3W-SOLGM and there are in total 5 simulation factors (sample size, group differences in intercept and slope, the covariance between the slope and intercept, size of time-specific residual, change the pattern of time-specific residual). Three main types of evaluation indices were used to assess the quality of estimation (bias/relative bias, standard error, and power/type I error rate). The results in the supplementary study show that the performance of 3W-LCFM and 3W-LCSM are equivalent, which further justifies the different models' comparison in the main study. The point estimates for the fixed effect parameters obtained from the two-wave models are unbiased or identical to the ones from the three-wave model. However, using two-wave models could reduce the estimation precision and statistical power when the time-specific residual variance is large and changing pattern is heteroscedastic (non-constant). Finally, two real datasets were used to illustrate the simulation results.
- Implementation of the Department of Housing and Urban Development’s Smoke-Free Rule: A Socio-Ecological Qualitative Assessment of Administrator and Resident PerceptionsHorn, Kimberly; Johnson, Sallie B.; Rincón-Gallardo Patiño, Sofía; Krost, Kevin; Gray, Tiffany; Dearfield, Craig; Du, Chenguang; Bernat, Debra (MDPI, 2021-08-24)In July 2018, the United States Department of Housing and Urban Development (HUD) implemented a mandatory smoke-free rule in public housing. This study assessed administrator and resident perceptions of rule implementation during its initial year in the District of Columbia Housing Authority (DCHA). Assessment included nine focus groups (n = 69) with residents and in-depth interviews with administrators (n = 7) and residents (n = 26) from 14 DCHA communities (family = 7 and senior/disabled = 7). Semi-structured discussion guides based on the multi-level socio-ecological framework captured dialogue that was recorded, transcribed verbatim, and coded inductively. Emerging major themes for each socio-ecological framework level included: (1) Individual: the rule was supported due to perceived health benefits, with stronger support among non-smokers; (2) Interpersonal: limiting secondhand smoke exposure was perceived as a positive for vulnerable residents; (3) Organizational: communication, signage, and cessation support was perceived as a need; (4) Community: residents perceived mobility, disability, weather, and safety-related issues as barriers; and (5) Public Policy: lease amendments were perceived as enablers of rule implementation but expressed confusion about violations and enforcement. A majority of administrators and residents reported favorable implications of the mandated HUD rule. The novel application of a socio-ecological framework, however, detected implementation nuances that required improvements on multiple levels, including more signage, cessation support, clarification of enforcement roles, and addressing safety concerns.
- Multilevel Analysis of Factors Associated with Left Behind Children in ChinaDu, Chenguang; Du, Hongfei (Canadian Center of Science and Education, 2020-09-24)With the rapid development of urbanization in China, a growing number of rural workers migrate to urban cities for employment opportunities with leaving their children at home. These children are called left behind children (LBC) in China and their population has dramatically increased during the last 20 years. So far, many studies have examined what factors were associated with this increasing LBC populations. However, they were rarely guided by a holistic perspective. The current study investigated 1,691 left behind children in 166 communities using data from the China Health and Nutrition Survey (CHNS) in 2011. Based on the human ecology theory, this study explored family and contextual (community) characteristics associated with the left behind children (LBC) in China. The main results for this subpopulation of families with children revealed stark contrasts with the literature for the general population of migrants. That is, for the families with children, (1) contrary to the literature, father‟s education was negatively associated with the probability of LBC at the individual level, even after the income was controlled; (2) community average father‟s education was also negatively associated with LBC; but (3) community average household income was not associated with LBC once the average father's education was controlled. The policy implications of these results are briefly discussed.
- Peer Support as a Mediator between Bullying Victimization and DepressionDu, Chenguang; DeGuisto, Kara; Albright, Jordan; Alrehaili, Sara (Canadian Center of Science and Education, 2018-02-21)Bullying has been one of the most common forms of school violence in the world. Many studies have shown that victims of bullying suffer from serious psychological issues. In the current study, the relationships between three variables: bullied victim, peer support, and depression symptom were assessed, using published data from the 2009–2010 Health Behavior in School-Aged Children Survey (N = 12,642). The data was collected from 314 public, Catholic, and other private schools in the United States that enrolled students from grades 5, 6, 7, 8, 9, and 10 or their equivalent in 50 states and the District of Columbia. The results indicated: (1) bullied victim was positively associated with depression symptom, with higher victimization score reporting higher depression symptoms; (2) bullied victim was negatively associated with peer support, with higher victimization score reporting lower peer support; (3) peer support was negatively related to depression symptoms; and (4) peer support partially mediates the relationship between victimization and depression symptoms among bullied students. This empirical study underscores the important role of peer support in mitigating the negative effects of bullying on the victim’s depression symptoms, which also provide empirical support for intervention programs based on the peer support system.
- Relational Language Improves Preschool Children’s Performance of Analogical ReasoningDu, Chenguang; Miyazaki, Yasuo; Cook, Michael; Papadopoulos, Joanna; Hao, Yuan (Canadian Center of Science and Education, 2018-05-08)The current study explored how relational language influenced the analogical reasoning among preschool children in China. Children (aged 4.5 and 5.5) in Experiment 1 were asked to complete a cross-mapped task where the object match competed with the relational match. The ANOVA results showed that the performance of both 4.5-year-olds and 4.5-year-olds were significantly improved after they heard Relational Language, F (1, 68) =44.821, p<0.05, η²=0.40. In Experiment 2, different distractors were added to the cross-mapped task and the 5.5-year-olds were replaced by 3.5 year-olds. The results demonstrated that the facilitating effect of Relational Language still existed among the youngest children and the performance of 4.5-year-olds was better than the 3.5-year-olds, F(1, 68)=6.76, p<0.05, η²=0.09. Furthermore, both age groups performed the worst under the distractor condition, indicating that the distractors made analogical reasoning more difficult, especially for the youngest children. Taken together, the current findings suggested that the facilitating effects of relational language in relational reasoning could also be observed in a broader sample.