Copper price prediction using LSTM recurrent neural network integrated simulated annealing algorithm.

Copper is an important mineral and fluctuations in copper prices can affect the stable functioning of some countries' economies. Policy makers, futures traders and individual investors are very concerned about copper prices. In a recent paper, we use an artificial intelligence model long short-term memory (LSTM) to predict copper prices. To improve the efficiency of long short-term memory (LSTM) model, we introduced a simulated annealing (SA) algorithm to find the best combination of hyperparameters. The feature engineering problem of the AI model is then solved by correlation analysis. Three economic indicators, West Texas Intermediate Oil Price, Gold Price and Silver Price, which are highly correlated with copper prices, were selected as inputs to be used in the training and forecasting model. Three different copper price time periods, namely 485, 363 and 242 days, were chosen for the model forecasts. The forecast errors are 0.00195, 0.0019 and 0.00097, respectively. Compared with the existing literature, the prediction results of this paper are more accurate and less error. The research in this paper provides a reliable reference for analyzing future copper price changes.

Evaluation of teaching method for fluid mechanics course in engineering education.

The professional technology training of student is the important objective of engineering education, which could present the specialized ability in the future. This task is conducted to evaluation of teaching methods for fluid mechanics course in the mechanical engineering. With the teaching practice, the advantage of teaching method is found, and the teaching quality can be revealed by the scores of integrated test. The improvement of teaching quality is contribute the development of social. According to the self-assessment, the effects of teaching method on the professional course is revealed.•The diversified teaching method is advantage to the understanding of theory and knowledge of application.•The practical training is suitable to develop the inner potential and innovation of different students.•The method allows the investigation of teaching method evaluation for the other courses with practicality.

Dynamic nexus between energy consumption, economic growth, and urbanization with carbon emission: evidence from panel PMG-ARDL estimation.

Carbon emission has been documented as a significant component of greenhouse gas that has been a significant source of environmental distortion globally. Based on panel data of 15 nations from 1980 to 2017, this study empirically investigates the impact of energy consumption, economic growth, urbanization, and energy consumption on carbon emission using panel co-integration tests and pooled mean group ARDL (PMG-ARDL) techniques. We augment the model with urbanization to establish the role urbanization plays in energy consumption, economic growth, and carbon emission nexus. Findings confirm that in the long run and short run, urbanization has no significant effect on the environment quality. On the other hand, energy consumption was found to enhance environmental destruction significantly in the short run and long run. Additional findings confirmed that economic growth causes environmental distortion in the long run for the sampled nations. Government officials and policymakers need to pay special attention to enhance adequate energy, urban planning, and emission reduction without affecting the economic development to achieve urban-economic-energy sustainability, which is key to attaining a green and clean environment.

Temperature Field in the Heat Transfer Process of PEEK Thermoplastic Composite Fiber Placement.

Under the effect of different process parameters, the temperature field inside the thermoplastic fiber is very complex and directly affects the fusion quality between the resins. Considering the heat transfer behavior of thermoplastic fiber polyether ether ketone (PEEK) as the research object, a mathematical model of heat transfer in the thermoplastic composite fiber placement with the relevant boundary conditions was established. Ansys Parametric Design Language (APDL) was used to generate the finite element model and simulate the transient process, not only to explore the influence of various process parameters on the temperature field, but also to build an online temperature field measurement system. The influence rules of placement process parameters and mold initial temperature with respect to the temperature field in the first layer were obtained. Combining the relationship between heating temperature and placement speed, when the first layer was laid, the placement process temperature could be quickly reached by low speed and high temperature. The temperature data were collected by the online detection system. Compared with the temperature data from the simulation, the error was below 8%, which verified the correctness of the heat transfer model. The academic research results will lay a theoretical foundation for the thermoplastic fiber placement.

[Effect of thermal cycling on surface microstructure of different light-curing composite resins].

OBJECTIVE: To evaluate the effect of thermal cycling on surface microstructure of different light-curing composite resins. METHODS: A nanofilled composite (Z350) and 4 microhybrid composites (P60, Z250, Spectrum, and AP-X) were fabricated from lateral to center to form cubic specimens. The lateral surfaces were abrased and polished before water storage and 40 000 thermal cycles (5/55 degrees celsius;). The mean surface roughness (Ra) were measured and compared before and after thermal cycling, and the changes of microstructure were observed under scanning electron microscope (SEM). RESULTS: Significant decreases of Ra were observed in the composites, especially in Spectrum (from 0.164±0.024 µm to 0.140±0.017 µm, P<0.001) and Z250 (from 0.169±0.035 µm to 0.144±0.033 µm, P<0.001), whose Ra approximated that of P60 (0.121±0.028 µm) with smoothly polished surface. SEM revealed scratches and shallower pits on the surface of all the 5 resins, and fissures occurred on Z350 following the thermal cycling. CONCLUSION: Water storage and thermal cycling may produce polishing effect on composite resins and cause fissures on nanofilled composite resins.

[Comparison of surface roughness of nanofilled and microhybrid composite resins after curing and polishing].

OBJECTIVE: To compare the surface roughness of nanofilled dental composite resin and microhybrid composite resins after curing and polishing. METHODS: A nanofilled composite (Z350) and 4 microhybrid composites (P60, Z250, Spectrum, and AP-X) were fabricated from the lateral to the medial layers to prepare 8 mm×8 mm×5 mm cubical specimens. The 4 lateral surfaces of each specimens were polished with abrasive disks (Super-Snap). Profilometer was used to test the mean surface roughness (Ra) after polishing. RESULTS: P60 had the lowest Ra (0.125∓0.030 µm) followed by Z250 and Spectrum. The Ra of Z350 (0.205∓0.052 µm) was greater than that of the other 3 resins, and AP-X had the roughest surfaces. Under scanning electron microscope, the polished faces of P60 resin were characterized by minor, evenly distributed particles with fewer scratches; the polished faces of Z350 presented with scratches where defects of the filling material could be seen. CONCLUSION: The nanofilled composite Z350 has smooth surface after polishing by abrasive disks, but its smoothness remains inferior to that of other micro-hybrid composite resins.

[Effect of caspase-dependent pathway on apoptosis of human gingival fibroblasts induced by advanced glycation end products].

OBJECTIVE: To investigate the effect of synthesized advanced glycation end products (AGE) on apoptosis of human gingival fibroblasts (HGF) and the possible role of caspase-dependent pathway in the process of AGE-induced apoptosis. METHODS: HGF were incubated with AGE-human serum albumin (AGE-HSA). The activity of caspase-8, caspase-9 and caspase-3 were detected by microplate reader after 12 and 24 hours. HGF were incubated with caspase inhibitors for 1 hour, and then incubated with AGE-HSA for 24 hours, HGF was first stained by Hoechst33258 and observed under inverted microscope, and then double stained by annexin V and propidine iodide (PI) and observed by flow cytometry (FCM). The activity of caspase-3 was determined by caspase-3 assay kit and observed by microplate reader. RESULTS: Caspases activity of caspase-8, -9, -3 was 0.1097 ± 0.0051, 0.0965 ± 0.0051 and 0.1280 ± 0.0103 after 12 h of incubation with AGE-HSA and HGF, respectively, and 0.1558 ± 0.0053, 0.1308 ± 0.0035 and 0.1954 ± 0.0051 after 24 h of incubation with AGE-HSA and HGF, respectively (P < 0.05). Positive cells number was 247.7 ± 32.4, 200.1 ± 14.6, 154.1 ± 14.4 and 131.3 ± 14.6 in caspase inhibitor groups by Hoechst33258 staining, respectively. Apoptotic rate was (25.57 ± 2.20)%, (38.87 ± 3.31)%, (17.17 ± 2.24)% and (14.73 ± 2.48)% in caspase inhibitor groups by annexin V-PI staining, respectively. The difference between different groups was significant (P < 0.05). Caspase-3 activity was reduced to 0.1274 ± 0.0076, 0.1465 ± 0.0062, 0.1044 ± 0.0051 in caspase inhibitor groups, respectively. The difference between different groups was significant (P < 0.05). CONCLUSIONS: Apoptosis of HGF induced by AGE-HSA may be mainly through activation of caspase-dependant pathway in which cytoplasmic pathway may play a predominant role.