Geotechnical properties of yellow silty sand soil modified by bio-stimulation with presence of NiCl2

Microbiologically induced calcite precipitation (MICP) is now widely tried to improve the quality of mostly sandy soil due to its application prospect to sustainability, environment-friendly and cost-efficiency. The present study is aiming to evaluate the feasibility of bio-stimulation, one of MICP techniques, for strengthening the engineering quality of Shanghai silty sand soil, a special type of soil located in low hillside of west Shanghai, as well as the influence of two factors: CaCl2 as a cementing material and NiCl2 as a co-factor, which was rarely researched before and can be viewed as the influence of urease activity on bio-stimulation result. The direct shear test, unconfined compressive test, supersonic wave test and calcite mass test have been carried out to evaluate engineering performance of yellow silty sand soil enhanced by bio-stimulation method as well as their relationship with concentration of CaCl2 and NiCl2 solutions. The result shows that bio-stimulation method can significantly promote the characteristics of Shanghai yellow silty sand soil and there seems to be extreme point for concentration of CaCl2 and NiCl2 solution in improving the quality of Shanghai yellow silty sand. Microstructure and composition of treated soil by bio-stimulation method have also been analyzed by Scanning Electron Microscope (SEM) and Energy dispersive Spectrometer (EDS), with giving the corresponding micro-mechanism of bio-cementation among soil particles.

DO INDONESIAN GOVERNMENT DEPLOY RELIABLE AMMUNITION FOR COVID-19 MASS TEST? A COMPARISON OF REAL-TIME PCR KITS

Objective: This study aimed to compare the level of reliability of three commercial real-time PCR kits in determining clinical samples. Methods: A total of 40 swabs samples which were previously tested positive, were re-test using the BioCov-19 RT-PCR kit, Sansure coronavirus disease 19 (COVID-19) nucleic acid diagnostic kit, and Kogen PowerCheck with Thermocycler (Roche). The amplification procedure is carried out based on the manual for each kit. Results: Sansure COVID-19 nucleic acid diagnostic was able to detect 40 samples with positive severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) results detected in both genes, while the PowerChek™ 2019-nCoV real-time PCR kit able to detect 35 samples showed that SARS-COV-II was detected in both genes, and the BioCoV-19 RT-PCR Kit brand kit able to detect 34 samples showed positive SARS-COV-2 results in both genes. Conclusion: The three commercial kits show great ability detection, so that they can be used to detect the presence of SARS-COV-II in clinical samples, and also in mass screening.

Threshold analyses on rates of testing, transmission, and contact for COVID-19 control in a university setting

We simulated epidemic projections of a potential COVID-19 outbreak in a university population of 38,000 persons, under varying combinations of mass test rate (0% to 10%), contact trace and test rate (0% to 50%), transmission rate (probability of transmission per contact per day), and contact rate (number of contacts per person per day). We simulated four levels of transmission rate, 14% (average baseline), 8% (average for face mask use), 5.4% (average for 3ft distancing), and 2.5% (average for 6ft distancing and face mask use), interpolating results to the full range to understand the impact of uncertainty in effectiveness, feasibility, and adherence of face mask use and physical distancing. We evaluated contact rates between 1 and 25, to identify the threshold that, if exceeded, could lead to several deaths. When transmission rate was 8%, for trace and test at 50%, the contact rate threshold was 8. However, any time delays in trace, test, and isolation quickly raised the number of deaths. Keeping contact rate to 3 or below was more robust to testing delays, keeping deaths below 1 up to a delay of 5 days from the time of infection to diagnosis and isolation. For a contact rate of 3, the number of trace and tests peaked to about 70 per day and relaxed to 25 with the addition of 10% mass test. When transmission rate was 5.4%, for trace and test at 50%, the contact rate threshold was 10. However, keeping contact rate to 4 or below was more robust to delays in testing, keeping deaths below 1 up to a delay of 6 days from the time of infection to diagnosis and isolation. For contact rate of 4, the number of trace and tests peaked at 50 per day and relaxed to 10 per day with the addition of 10% mass test. Threshold estimates can help develop on-campus scheduling and indoor-spacing plans in conjunction with plans for asymptomatic testing for COVID-19. Combination thresholds should be selected specific to the setting based on an assessment of the feasibility and resource 48 availability for testing and quarantine.

Behavior of Small Variable Mass Particle in Electromagnetic Copenhagen Problem

The paper presents the behavior of the motion properties of the variable mass test particle (third body), moving under the influence of the two equal primaries having electromagnetic dipoles. These primaries move on the same circular path around their common center of mass in the same plane. We have determined the equations of motion of the test particle whose mass varies according to Jean's law. Using the system of equations of motion we have evaluated the locations of equilibrium points, their movements and basins of the attracting domain. Finally, we examine the stability of these equilibrium points, all of which are unstable.

DEVELOPMENT OF A METHOD FOR ASSESSING LEARNING OUTCOMES THROUGH AUTOMATED TESTING MANAGEMENT

Testing knowledge is an important part of the pedagogical process, as it helps to improve the quality of professional knowledge, contributes to the effectiveness and efficiency of training. This article discusses the use of several approaches to building a fuzzy diagnostic expert system for knowledge testing. The aim of the research is a comprehensive optimisation of the process of mass test information processing in order to obtain reporting data, consideration of clear and fuzzy tests, drawing the analogy between clear and fuzzy tests, proposal and justification of different schemes of summing up the testingandproposal of one's own prototype of automated expert testing system which covers all stages of the testing process. Generally speaking, testing, as an algorithmic problem, can be represented as a problem of building an expert system to evaluate knowledge of testees. Such systems are used in solving many problems related to effective management, scientific research, and the like, where it is necessary to get the result with a limited amount of reliable information. It is established that the classical theory of tests has a number of controversial assumptions, and the results of its application have serious practical drawbacks. Therefore, the main principle of the approach in the work is the separation of the creation of a bank of test tasks and the process of compiling tests (bank of test material) and testing.

Impact of Experimental Parameters on Degradation Mechanism and Service Life Prediction of CFRP Anode during Simulated ICCP Process

In actual building structure, it usually takes tens of years for the degradation to be significantly observed during impressed current cathodic protection (ICCP) process. Thus, simulated ICCP with aqueous electrolyte (instead of concrete) was used as an accelerated method to study degradation mechanism and make service life prediction. In this work, the impact of parameters including current (density) and NaCl electrolyte concentration on the degradation mechanism and service life prediction was evaluated for a simulated ICCP system with CFRP as anode. Experiments were performed with different levels of applied current (4, 10, and 20 mA) as well as with different NaCl electrolyte concentrations (3, 10, and 20% by mass). Test results showed that under all the designed conditions, both chlorination and oxidation reaction occurred during the simulated ICCP process, ensuring consistency of mechanism. From the aspect of service life prediction of CFRP, it was found that the system was not sensitive to the concentration of NaCl electrolyte but was much more influenced by the current (density) applied. Thus, for the simulated ICCP system, the current (density) should be carefully chosen since a tiny change in level of current may cause a large variation in service life prediction.