Construction phase oriented dynamic simulation: taking RCC dam placement process as an example

Construction simulation has been widely applied in schedule analysis. However, traditional simulation is based on static models built in the planning or design phase, which focuses on overall project-level schedule analysis. To provide activity-level simulation for on-site schedule management, a construction phase oriented dynamic simulation method is proposed, which takes roller compacted concrete (RCC) dam placement process as an example. Considering various innerlayer and inter-layer activities and different construction organization modes, a detailed placement process simulation model is built. Based on construction data collected by real-time monitoring, a construction activity modeling method is given. Additionally, Dirichlet process mixture (DPM) models are applied for simulation parameter updates, which endows density estimation with considerable flexibility and robustness. A fast inference algorithm is also proposed to realize the fast posterior computation of DPM models. The proposed method is tested by an RCC dam project in southwest China. The results show that the proposed method can reflect the dynamic features of the actual placement process in the construction phase and provide accurate schedule predictions for on-site construction management

An Estimated <inline-formula><math display="inline"><semantics><mi>δ</mi></semantics></math></inline-formula>-Based Iterative Block Decision Feedback Equalization in SC-FDE System

We provide a novel nonlinear frequency domain equalization algorithm for the frequency domain equalization of an SC-FDE system by improving the classical iterative block decision feedback equalization (IBDFE) algorithm and applying δ estimation to the improved algorithm. The improvement of the IBDFE algorithm is carried out by replacing the ZF equalization in the feedback branch with the MMSE equalization and eliminating the iteration of the correlation factor, thus reducing the noise error and the computational complexity of the original algorithm. δ estimation can estimate residual inter-symbol interference in the signal after MMSE equalization and reject it, thus further improving the equalization accuracy. The simulation results show that the performance of the novel algorithm is better than that of the IBDFE algorithm with similar complexity, or the complexity of the novel algorithm is lower than that of the IBDFE algorithm with similar performance

An Unusual Complication of Self-Expandable Metal Stent Placement in Malignant Sigmoid Obstruction

Self-expandable metal stent (SEMS) for malignant colorectal obstruction is widely used as a bridge to elective surgery or palliative treatment. However, with the increasing use of SEMS for treatment, complication rates associated with stents have been raised as a concern. We experienced a rare migration-related complication that a stent partially migrated out of the anus with an incarceration. A 62-year-old man was admitted with sigmoid malignant obstruction. Due to multiple metastases, he refused to undergo colostomy, and an uncovered SEMS was placed. Subsequently, he started chemotherapy. Seven months after placement, the stent migrated into the rectum. After unsuccessful attempts to extract the stent, he sought our assistance. We observed that half of the stent was outside the anus, and a 15 mm lump of mucosa was embedded in the proximal end of the stent. After several attempts, we successfully removed the SEMS. Stent incarceration following migration is not a common occurrence, but it serves as a reminder that clinicians need to be more vigilant about complications that may arise after stent implantation. We describe this unusual complication and share our experience about the removal of the stent

An Estimated &delta;-Based Iterative Block Decision Feedback Equalization in SC-FDE System

We provide a novel nonlinear frequency domain equalization algorithm for the frequency domain equalization of an SC-FDE system by improving the classical iterative block decision feedback equalization (IBDFE) algorithm and applying &delta; estimation to the improved algorithm. The improvement of the IBDFE algorithm is carried out by replacing the ZF equalization in the feedback branch with the MMSE equalization and eliminating the iteration of the correlation factor, thus reducing the noise error and the computational complexity of the original algorithm. &delta; estimation can estimate residual inter-symbol interference in the signal after MMSE equalization and reject it, thus further improving the equalization accuracy. The simulation results show that the performance of the novel algorithm is better than that of the IBDFE algorithm with similar complexity, or the complexity of the novel algorithm is lower than that of the IBDFE algorithm with similar performance

Comparison of Different Methods to Estimate Canopy Water Storage Capacity of Two Shrubs in the Semi-Arid Loess Plateau of China

The canopy water storage capacity of vegetation has great significance for the hydrological cycle. We used the Pereira regression analysis method, scale-up method, and simulated rainfall method to determine canopy water storage capacity from 2014 to 2018. The Pereira regression analysis was affected mainly by the seasonal variation in the leaf area index and the observation method of throughfall. The canopy water storage capacity was 0.68 mm and 0.72 mm for C. korshinskii and H. rhamnoides, respectively. The canopy water storage capacity of C. korshinskii and H. rhamnoides was 0.73 mm and 0.76 mm, respectively, using the scale-up method. The scale-up method showed that water storage capacity per area of the canopy components was in the order of branches (0.31 mm) &gt; leaves (0.27 mm) &gt; trunks (0.15 mm) for C. korshinskii, and trunks (0.33 mm) &gt; branches (0.29 mm) &gt; leaves (0.14 mm) for H. rhamnoides. We used eight simulated rainfall intensities to determine the canopy water storage capacity for C. korshinskii and H. rhamnoides, which was 0.63 mm and 0.59 mm, respectively

Comparison of Different Methods to Estimate Canopy Water Storage Capacity of Two Shrubs in the Semi-Arid Loess Plateau of China

The canopy water storage capacity of vegetation has great significance for the hydrological cycle. We used the Pereira regression analysis method, scale-up method, and simulated rainfall method to determine canopy water storage capacity from 2014 to 2018. The Pereira regression analysis was affected mainly by the seasonal variation in the leaf area index and the observation method of throughfall. The canopy water storage capacity was 0.68 mm and 0.72 mm for C. korshinskii and H. rhamnoides, respectively. The canopy water storage capacity of C. korshinskii and H. rhamnoides was 0.73 mm and 0.76 mm, respectively, using the scale-up method. The scale-up method showed that water storage capacity per area of the canopy components was in the order of branches (0.31 mm) > leaves (0.27 mm) > trunks (0.15 mm) for C. korshinskii, and trunks (0.33 mm) > branches (0.29 mm) > leaves (0.14 mm) for H. rhamnoides. We used eight simulated rainfall intensities to determine the canopy water storage capacity for C. korshinskii and H. rhamnoides, which was 0.63 mm and 0.59 mm, respectively

The effects of rainfall characteristics and land use and cover change on runoff in the Yellow River basin, China

The changes of runoff in the middle reaches of the Yellow River basin of China have received considerable attention owing to their sharply decline during recent decades. In this paper, the impacts of rainfall characteristics and land use and cover change on water yields in the Jingle sub-basin of the middle reaches of the Yellow River basin were investigated using a combination of statistical analysis and hydrological simulations. The Levenberg Marquardt and Analysis of Variance methods were used to construct multivariate, nonlinear, model equations between runoff coefficient and rainfall intensity and vegetation coverage. The land use changes from 1971 to 2017 were ascertained using transition matrix analysis. The impact of land use on water yields was estimated using the M-EIES hydrological model. The results show that the runoff during flood season (July to September) decreased significantly after 2000, whereas slightly decreasing trend was detected for precipitation. Furthermore, there were increase in short, intense, rainfall events after 2000 and this rainfall events were more conducive to flood generation. The “Grain for Green” project was carried out in 1999, and the land use in the middle reaches of the Yellow River improved significantly, which make the vegetation coverage (Vc) of the Jingle sub-basin increased by 13%. When Vc approaches 48%, the runoff coefficient decreased to the lowest, and the vegetation conditions have the greatest effect on reducing runoff. Both land use and climate can change the water yield in the basin, but for areas where land use has significantly improved, the impact of land use change on water yield plays a dominant role. The results acquired in this study provide a useful reference for water resources planning and soil and water conservation in the erodible areas of the middle reaches of the Yellow River basin

Relationship among oil and gas resources, reserves and production in China and suggestions for the development direction of national oil and gas resource assessment

In order to understand the connotation and substantive relationship among oil and gas resources, reserves and production on a deeper level, this paper made an in-depth analysis and elaboration on the relationship among the three from the perspectives of theoretical logic and practical transformation, and presented suggestions for the development direction of resource assessment based on the analysis of application status. Resources, reserves and production are estimated quantities of oil and gas mineral resources under different levels of understanding. In China's classification system, reserves and resources are in a parallel relationship, and reserves and production are in an inclusive relationship. Both resources and reserves are geological meanings. The transformation from resources to reserves is affected by factors such as national spatial planning, mining right setting, theoretical technical and economic conditions, and the transformation from reserves to production is affected by factors such as reserves upgrading and transformation, whether to convert to mining, recovery factor, etc. China still has some deficiencies in resource assessment and release, as well as quantitative prediction of resources, reserves and production, which is also an important reason for the cognitive confusion of "China has rich resource potential but it is difficult to increase reserves and production". The enrichment and development of resource assessment contents and results application analysis will help to form a comprehensive and in-depth understanding of the current situation of oil and gas resources. It should be further explored and developed in the future from the following respects: mobility classification of assessment results, assessment of (undiscovered) recoverable resources and application analysis of results