Plasmonic colloidal nanoparticles with open eccentric cavities via acid-induced chemical transformation

Surface-enhanced Raman spectroscopy (SERS) has been considered a promising technique for the detection of trace molecules in biomedicine and environmental monitoring. The ideal metal nanoparticles for SERS must not only fulfill important requirements such as high near-field enhancement and a tunable far-field response but also overcome the diffusion limitation at extremely lower concentrations of a target material. Here, we introduce a novel method to produce gold nanoparticles with open eccentric cavities by selectively adapting the structure of non-plasmonic nanoparticles via acid-mediated surface replacement. Copper oxide nanoparticles with open eccentric cavities are first prepared using a microwave-irradiation-assisted surfactant-free hydrothermal reaction and are then transformed into gold nanoparticles by an acidic gold precursor while maintaining their original structure. Because of the strong near-field enhancement occurring at the mouth of the open cavities and the very rough surfaces resulting from the uniformly covered hyperbranched sharp multi-tips and the free access of SERS molecules inside of the nanoparticles without diffusion limitation, adenine, one of the four bases in DNA, in an extremely diluted aqueous solution (1.0 pM) was successfully detected with excellent reproducibility upon laser excitation with a 785-nm wavelength. The gold nanoparticles with open eccentric cavities provide a powerful platform for the detection of ultra-trace analytes in an aqueous solution within near-infrared wavelengths, which is essential for highly sensitive, reliable and direct in vivo analysis.None1132sciescopu

3D geo-cellular modeling for Oligocene reservoirs: a marginal field in offshore Vietnam

This study focuses on constructing a 3D geo-cellular model by using well-log data and other geological information to enable a deep investigation of the reservoir characteristics and estimation of the hydrocarbon potential in the clastic reservoir of the marginal field in offshore Vietnam. In this study, Petrel software was adopted for geostatistical modeling. First, a sequential indicator simulation (SIS) was adopted for facies modeling. Next, sequential Gaussian simulation (SGS) and co-kriging approaches were utilized for petrophysical modeling. Furthermore, the results of the petrophysical models were verified by a quality control process before determining the in-place oil for each reservoir in the field. Multiple geological realizations were generated to reduce the geological uncertainty of the model assessment for the facies and porosity model. The most consistent one would then be the best candidate for further evaluation. The porosity distribution ranged from 9 to 22%. The original oil place of clastic reservoirs in the marginal field was 50.28 MMbbl. Ultimately, this research found that the marginal field could be considered a potential candidate for future oil and gas development in offshore Vietnam

Impacts of injection temperature on the relevant heat transport processes in groundwater heat pump (GWHP) systems

In many hydrogeological applications, the influence of temperature on fluid density and viscosity have often been neglected. However, high contrasts in temperature which occurs in the field applications such as groundwater heat pump (GWHP) systems, can make the effects of variable density and viscosity on flow and transport significant. A theoretical study suggests that free convection occurs in an infinitely extensive horizontal layer when the Rayleigh number exceeds about 40. Experimental investigations are still lacking on the conditions where the influence of temperature can be important.In this study, a laboratory experimental system was developed to investigate the impacts of injection temperature on the relevant heat transport processes. First of all, the experiments such as sieve analysis and constant-head permeability test were performed to estimate the physical properties of the saturated porous medium. Laboratory tracer tests using a resistor as a heat source were conducted with/without background flow conditions to derive the thermal properties of the medium. Lastly, tracer tests using injected water with different temperatures were performed to identify the certain conditions where the variations in fluid density and viscosity play an important role in the subsurface flow and transport

Correction: 3D geo-cellular modeling for Oligocene reservoirs: a marginal field in offshore Vietnam

Correction to: Journal of Petroleum Exploration and Production Technology (2022) 12:1–19 https://doi.org/10.1007/s13202-021-01300-

Effect of Ceramic Dust as Partial Replacement of Cement on Lightweight Foamed Concrete

Disposal of waste into the landfill causes a severe impact on the environment. One of the waste products is ceramic waste. Ceramic waste has some excellent properties in its durability, hardness, and highly resistant to biological, chemical, and physical degradation forces. These excellent properties of the ceramic waste may make it suitable to be used in concrete. This study investigates the effect on the compressive strength of lightweight foamed concrete with different percentage of ceramic dust replacement level towards the cement and three different levels of water-cement ratio. 0%, 5%, 15%, and 25% of replacement level with 0.52, 0.56, and 0.60 water-cement ratios respectively for each replacement level was used as the parameter to investigate the fresh properties, and strength performance of lightweight foamed concrete. The stability and consistency of every mix are studied as well. From this study, it was observed that the incorporation of ceramic waste dust partially replaced the cement did not affect on the fresh properties of the foamed concrete. However, the compressive strength of foamed concrete affected by ceramic waste dust partially replaced the cement

Minimum well separation for small groundwater heat pump (GWHP) systems in Korea: Preliminary analysis based on regional aquifer properties

Shallow geothermal energy has been estimated to have an excellent applicability in Korea, and its applications for space heating and cooling have steadily increased in recent years. Such application as ground source heat pump (GSHP) system can be classified into closed- and open-loop. In recent years, studies have been conducted to minimize the environmental impacts resulting from pumping/injection and to enhance the efficiency of groundwater heat pump (GWHP) system that is the open-loop system. These studies suggest that the characteristics of the aquifer have a significant role in designing efficient GWHP systems. This study considers various hydrogeological properties of Korea. An open-source numerical code called TRS was used for preliminary and sensitivity analyses of GWHP systems. In the analyses, arrival time when thermal plume arrives at pumping well and temperature change at pumping well were observed with different pumping/injection rates, hydraulic gradient, and well separation. Thus, we derived adequate well arrangement for efficient GWHP operation

Reconstructing Daily Discharge in a Megadelta Using Machine Learning Techniques

In this study, six machine learning (ML) models, namely, random forest (RF), Gaussian process regression (GPR), support vector regression (SVR), decision tree (DT), least squares support vector machine (LSSVM), and multivariate adaptive regression spline (MARS) models, were employed to reconstruct the missing daily-averaged discharge in a mega-delta from 1980 to 2015 using upstream-downstream multi-station data. The performance and accuracy of each ML model were assessed and compared with the stage-discharge rating curves (RCs) using four statistical indicators, Taylor diagrams, violin plots, scatter plots, time-series plots, and heatmaps. Model input selection was performed using mutual information and correlation coefficient methods after three data pre-processing steps: normalization, Fourier series fitting, and first-order differencing. The results showed that the ML models are superior to their RC counterparts, and MARS and RF are the most reliable algorithms, although MARS achieves marginally better performance than RF. Compared to RC, MARS and RF reduced the root mean square error (RMSE) by 135% and 141% and the mean absolute error by 194% and 179%, respectively, using year-round data. However, the performance of MARS and RF developed for the climbing (wet season) and recession (dry season) limbs separately worsened slightly compared to that developed using the year-round data. Specifically, the RMSE of MARS and RF in the falling limb was 856 and 1, 040 m3/s, respectively, while that obtained using the year-round data was 768 and 789 m3/s, respectively. In this study, the DT model is not recommended, while the GPR and SVR models provide acceptable results

A Parallelized Model For Simulating A Vertical Closed-Loop Geothermal Heat Pump System

ABSTRACT A borehole heat exchanger (BHE) is one of the important factors that can affect performance of the vertical closedloop geothermal heat pump (GHP) system. Its construction costs are also a large percentage of the overall initial costs of the GHP system. When constructing BHEs, several parameters should be determined, such as length of the borehole heat exchanger, the number of the BHEs, and spacing between BHEs. Numerical simulation can be used to find optimal parameters. However, it takes a long time to find optimal parameters with a large domain. To reduce the calculation time, a massively parallel computing procedure is introduced into the serial simulator for the vertical closed-loop GHP system. It can simulate temperature changes in the BHE with circulating fluid through the Utubes and compute groundwater flow and aquifer temperature changes. By increasing the number of processors, the total execution time was reduced from 7,031 seconds using two processors to 1,145 seconds using 32 processors. The total execution time of the serial model is 13,902 seconds

Case study on high-resolution monitoring network of groundwater heat pump system

With the increasing installation of shallow geothermal energy, the importance of thermal impact prediction also increases in the system design stage. In nature, it is general that heterogeneity exists and it can affect the groundwater flow as well as the transport along to the flow. When predicting heat transport under the groundwater heat pump (GWHP) operation, however, impacts of heterogeneity have rarely been considered. In this study, to detect the hydraulic and thermal feedback to the two months of GWHP operation, a dense monitoring network was constructed with 12 monitoring wells at Eumseong-gun, Republic of Korea. The temperature was monitored in high resolution via fiber-optic distributed temperature sensing. During the GWHP operation, a very dynamic flow condition was generated with the hydraulic gradient between 0.005 and 0.07. The maximum temperature change at the nearest monitoring well was 2 ?. Observed hydraulic and thermal responses showed spatially heterogeneous results. While the heterogeneous responses of hydraulic change were stronger near the geothermal wells, those of temperature change were higher near the center of the thermal plume