bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability analysis for a class of mechanical systems with piecewise constant coefficients
Authors: Platonov Alexey 
Published: July 2021

Abstract
A nonlinear mechanical system described by a vector equation of the Lienard type is considered. It is assumed that the forces acting on the mechanical system are given by functions that are piecewise constant with respect to time. With the aid of a special variable substitution, the equation is reduced to a system that can be considered as an impulsive switched system with infinite numbers of operating modes. The stability problem for the trivial equilibrium position of the obtained system is studied. The stability analysis is carried out using a specially constructed discontinuous Lyapunov function. This function can be understood as a multiple Lyapunov function, consisting of an infinite number of partial Lyapunov functions, each of which is used for a certain time interval. Differentiating the chosen Lyapunov function with respect to solutions of the given system on the corresponding time intervals and applying the theory of differential inequalities, sufficient conditions of the asymptotic stability of the equilibrium position are established.
Experimental studies of wedge models
Authors: Ruleva L B , Solodovnikov S I 
Published: July 2021

Abstract
The functionality of the more complete validation of the developed CDF is being expanded for “Hypersonic aerodynamic shock tube” laboratory facilities. Models of triple semi-wedge with sharp edge and blunt edges were tested. The regions of the high pressure close to the blunted edge of the model are revealed. In the upper model, the greatest pressure was detected on the front face and in the middle region of the flat channel. The experimental graphs of the pressure distribution on the upper and lower surfaces of the model are compared with numerical simulations at limited distances from the nozzle section.
The collection of mechanisms by P.L. Chebyshev at the department of theoretical and applied mechanics of St. Petersburg university
Authors: Tovstik P E , Yushkov M P , Kuteeva G A , Sinilshchikova G A , Trifonenko B V 
Published: July 2021

Abstract
The paper presents some information and photos dealing with mechanisms by the great Russian mathematician P.L. Chebyshev. These mechanisms are kept at the revived Cabinet of Practical Mechanics of the History of Physics and Mathematics Museum of St. Petersburg State University (SPBU). This revived cabinet is now located at the Mathematics and Mechanics Faculty of SPBU in Peterhof.
Influence of electric charge on surface of a solar sail on dy-namics of the sail which moves along Tsander’s trajectories
Authors: Yakovlev A B 
Published: July 2021

Abstract
The application of a solar sail spacecrafts for a realization of distant flights into a space is actively discussed. However, all bodies in space plasma get electric charge which depends on density and temperature of plasma, a stream of sunlight and electro-physical characteristics of a body. But till now not enough attention has been given a problem of influence of the charging of a solar sail on its dynamics and durability characteristics. The charging of thin films, such as a solar sail has a number of features. Most important of them are: 1) a surface is bilateral and not closed, 2) partial permeability of a film for the charged particles of a space environment. In this work there are the results of calculations of electric charge density on the surface of the solar sail in the space between orbits of the Earth and Jupiter and an estimate of influence of electric charge of a sail on dynamics of solar sail spacecrafts which moves along elliptic Tsander’s a trajectory. The problem about deflection determination is reduced to integration of one-dimensional problem of the motion of a body with variable acceleration. The obtained estimates of the influence of an electric charge induced on the surfaces of the solar sail on the motion of a space vehicle during interplanetary flights along the orbits mentioned above have shown that the influence is small.
Heat-health vulnerabilities in the climate change context—comparing risk profiles between indoor and outdoor workers in developing country settings
Authors: Venugopal Vidhya , Shanmugam Rekha , Perumal Kamalakkannan Latha 
Published: July 2021

Abstract
Occupational heat stress is a crucial risk factor for a range of Heat-Related Illnesses (HRI). Outdoor workers in unorganized work sectors exposed to high ambient temperatures are at increased risk in developing countries. We aim to compare HRI, Productivity Loss (PL), and reduced renal health risk between workers from outdoor unorganized (N = 1053) and indoor organized (N = 1051) work sectors. Using descriptive methods and a large epidemiological cross-sectional study using mixed methods, we compared risk patterns between the two groups. We analyzed the risk of self-reported HRI symptoms, Heat Strain Indicators (HSIs), PL, and reduced kidney function using Multivariate Logistic Regression (MLR) models. Although Wet Bulb Globe Temperature (WBGT) exposures were high in both the outdoor and indoor sectors, significantly more Outdoor Unorganized Workers (OUWs) reported heat stress symptoms (45.2% vs 39.1%) among 2104 workers. OUWs had a significantly higher share of the heavy workload (86.7%) and long years of heat exposures (41.9%), the key drivers of HRIs, than the workers in indoor sectors. MLR models comparing the indoor vs outdoor workers showed significantly increased risk of HRI symptoms (Adjusted Odds Ratio) (AORoutdoor = 2.1; 95% C.I:1.60–2.77), HSI (AORoutdoor = 1.7; 95% C.I:1.00–2.93), PL (AORoutdoor = 11.4; 95% C.I:7.39–17.6), and reduced kidney function (Crude Odds Ratio) (CORoutdoor = 1.4; 95% C.I:1.10–1.84) for the OUWs. Among the heat-exposed workers, OUW had a higher risk of HRI, HSI, and PL even after adjusting for potential confounders. The risk of reduced kidney function was significantly higher among OUWs, particularly for those with heat exposures and heavy workload (AORoutdoor = 1.5; 95% C.I: 0.96–2.44, p = 0.073) compared to the indoor workers. Further, in-depth studies, protective policies, feasible interventions, adaptive strategies, and proactive mitigation efforts are urgently needed to avert health and productivity risks for a few million vulnerable workers in developing nations as climate change proceeds.
Fermion sign problem in path integral Monte Carlo simulations: grand-canonical ensemble
Authors: Dornheim Tobias 
Published: July 2021

Abstract
We present a practical analysis of the fermion sign problem in fermionic path integral Monte Carlo (PIMC) simulations in the grand-canonical ensemble (GCE). As a representative model system, we consider electrons in a 2D harmonic trap. We find that the sign problem in the GCE is even more severe than in the canonical ensemble at the same conditions, which, in general, makes the latter the preferred option. Despite these difficulties, we show that fermionic PIMC simulations in the GCE are still feasible in many cases, which potentially gives access to important quantities like the compressibility or the Matsubara Greens function. This has important implications for contemporary fields of research such as warm dense matter, ultracold atoms, and electrons in quantum dots.
Assessment on shallot farming development in North Padang Lawas Regency, North Sumatra
Authors: Girsang Moral Abadi , Nainggolan Palmarum , Hidayat Shabil , Sitepu Suheri , Ramija Khadijah El 
Published: July 2021

Abstract
The purpose of this study was to obtain information on the existing shallot farming in North Padang Lawas Regency which includes the conditions of agricultural land for shallot, existing technology, and the income of farmers, then provides recommendations for shallot’s farming technology to increase shallot’ production, and to increase farmers’ income. The method used in this research were survey, field observation, and soil sampling. To determine the suitability of land for shallots, the evaluation of land suitability was carried out by comparing the quality/characteristics of the land with the requirements for shallot growth. Analysis of Land evaluation was carried out computerized using the SPKL version 2.01 software. Analysis of shallot farm income was carried out by analyzing the balance between revenue and cost. The results obtained from this study were the technology used by farmers was still simple, land suitability for shallots is dominated by marginal land suitability (S3) so that additional input is needed to increase production, while shallot farming was feasible with an R/C ratio level of 2,19.
K-Nearest Neighbor Algorithm to Identify Cucumber Maturity with Extraction of One-Order Statistical Features and Gray-Level Co-Occurrence
Authors: Syahrorini Syamsudduha , Syamsudin Denny , Saputra Dwi Hadidjaja Rasjid , Ahfas Akhmad 
Published: July 2021

Abstract
Determination of the maturity of cucumber fruit after harvest is subjective. The level of thoroughness of each individual’s cucumber selection is different. The maturity of cucumbers is seen from the age of the fruit, the resemblance of ripe cucumbers or old, raw or young is difficult to distinguish in terms of the texture of the fruit skin. The use of red, green, blue, and grayscale color modes from the cucumber imagery, is then processed using the extraction of the statistical features of the Order-One and Order-Two GLCM methods. Imagery using a 13 megapixels smartphone camera. Texture parameter values are used in the first order: mean, variance, skewness, kurtosis, entropy. Second order: energy, contrast, correlation, inverse different moments, angular second moments, variance 2, and entropy 2. The classification of the texture parameters of both order uses an algorithm from K-Nearest Neighbors as a comparison of test data values and training data. So that the system is made can identify the maturity of cucumbers old and young. The highest accuracy is found in grayscale imagery with a combination of two skewness and kurtosis parameters and euclidean distance calculation in K-Nearest Neighbor classification of 96.05%.
Sugarcane bagasse for environmentally friendly super-absorbent polymer: synthesis methods and potential applications in oil industry
Authors: Riswati Shabrina Sri , Setiati Rini , Kasmungin Sugiatmo , Prakoso Suryo , Fathaddin Muhammad Taufiq 
Published: July 2021

Abstract
Super-absorbent polymer (SAP) is able to absorb water by multiple times more than its own weight. Sugarcane bagasse (SCB) raw material has been excessively produced as a byproduct in sugar factory. The synthesis of SAP from SCB creates a balance between the utilization of industrial by-product and the resulted environmentally friendly material. In oil production water might be a troublesome, thus minimizing water production while extracting oil is essential. Besides, diversion of the flow in heterogeneous reservoir optimizes the oil production. SCB-SAP might have the potential to act as a water absorbing agent and flow diverter by taking the advantage of SAP high swelling ratio characteristic. This study provides the information of SCB-SAP synthesis methods and highlights the current application of SAP in oil industry, including the laboratory studies and field tests.
Petrophysical Analysis to Determine the Initial Oil Reserves in the AHP Field
Authors: Sudi Apolonius Harda Putranta , Sitaresmi Ratnayu , Yulia Prayang Sunny 
Published: July 2021

Abstract
Petrophysic analysis is carried out for the evaluation of petrophysical parameters. The aim of this paper is determine the initial oil in place (OOIP) by Volumetric method in the field that will be conducted research, such as reservoir thickness (h) or net pay, porosity (∅), and also water saturation (Sw). This parameter is used to position the initial oil reserves (OOIP) at two wells that will be examined, namely A1-R wells and A5-R wells. After qualitative analysis of both wells, namely A1-R well and A5-R well, it was seen that A1-R and A5-R, the litilogy well are dominated by limestone and After conducting qualitative analysis conducted quantitative analysis that is to find out the porosity (∅), resistivity, water resistivity, water saturation (Sw) and net pay (h) of the two wells. From the calculation, the porosity value is obtained by 19% in A1-R wells and the average porosity in A5-R wells is 26%, water saturation (Sw) from A1-R wells and A5-R wells are 34% and 28% and net pay (h) values are 2.82 at A1-R wells and 2.83 in A5-R wells. After the volumetric calculation, the OOIP value of A1-R well and A5-R well is 8826315.716 STB and 85308364.22 STB.
Compatibility Test for Screening Surfactant Flooding
Authors: Dhafa M , Setiati R , Malinda M T , Anugrahadi A 
Published: July 2021

Abstract
Surfactant flooding is one of the methods used in Enhanced Oil Recovery. The purpose of this study was to determine the suitability of a reservoir to the surfactant injection that will be carried out in that reservoir. Surfactants are used as a method to increase oil recovery because they are able to reduce the surface tension between the injecting fluid and the oil. Before selecting the surfactant material to be used, screening criteria must be done between the reservoir data and the surfactant. Reservoir data must match the requirements required for surfactant injection. After screening criteria, the next step is to test the compatibility of the surfactant fluid to the reservoir fluid. At this stage, it consists of a compatibility test, interfacial tension (IFT) test, and phase behavior test with the middle phase emulsion. Laboratory screening tests using test tubes, ovens and spinning drop. The fluids tested include the types of surfactants and crude samples. From the observations in this study, there are several results that can guide surfactant screening. Compatible surfactants are surfactants that clearly, form a middle phase emulsion and low IFT values. By conducting screening criteria, it can be concluded that the suitability of the reservoir represented by the crude oil sample against the surfactant that will be applied as the injection fluid.
Effect of Improvement of Temperature and Gas Amount on Nitrogen Flooding
Authors: Malinda M T , Setiati R , Azizi M A , Simbolon Y F 
Published: July 2021

Abstract
Oil and natural gas are energy resources with high demand, so it is very important to implement enhanced oil recovery technology in old fields to obtain optimum oil production. The enhanced oil recovery technology that will be discussed on this occasion is more specifically related to the gas flooding method, namely nitrogen flooding. Nitrogen flooding is currently used more often as an alternative to CO2 flooding. However, the limitation of this method is that it is only effective when used in a field with a high depth, because it requires a constant high pressure and temperature so that this gas can dissolve into the reservoir fluid. Therefore, it is necessary to conduct a more in-depth study of the nitrogen flooding method, so that its application can get optimal, efficient, and economical results. The results of laboratory research were carried out to study the displacement of crude oil using the high pressure nitrogen injection method. It aims to study the effect of temperature and GOR on crude oil recovery and the solubility process in high pressure nitrogen injection. In addition, the effectiveness of nitrogen injection after water flooding, and the effect of propane slug driven by nitrogen injection were also analyzed. There are nine types of experiments carried out using crude oil 42.3° API which is recombined with natural gas. This experiment used two temperatures, 70° F and 120° F, and three GORs, namely 575 scf/stb, 400 scf/stb, and 200 scf/stb. The reservoir model used was a stainless steel tube 125 feet long and 0.435 inches in diameter, packed with consolidated sand to provide an average permeability of 910 mD. The recovery factor in nitrogen injection is influenced by the gas content in the system. If the gas content is high, then nitrogen injection will result in a higher oil recovery compared to conditions where the gas content is low.
Drill Holes Spacing Analysis for Estimation and Classification of Coal Resources Based on Variogram and Kriging
Authors: Ramadhan M D , Marwanza I , Nas C , Azizi M A , Dahani W , Kurniawati R 
Published: July 2021

Abstract
In detailed exploration, it is necessary to analyze optimal drill hole distance. Drill hole spacing analysis results in optimal drill hole spacing on each coal seam for the coal resources classification. Based on a case study in one of the coal mining companies in North Bengkulu, four coal seams have continuous seams and there is splitting from one seam to four seams. The sediment model generally has a direction of distribution of coal seams trending from northeast to southwest with gentle dip. This research uses geostatistical methods to determine the thickness distribution and variation of coal in the study area and to estimate and classify coal resources and determine the optimal distance from the borehole spacing. Estimation using kriging block results in the value of kriging relative error. Coal resource estimates and variability are determined based on kriging estimation with the relative kriging standard deviation (RKSD) method and the polygon method for classification based on sill distances. The number of drill holes used was 57 drill holes. Based on the calculation of the sill variogram, the coal measured resource is 150 meters, the coal indicated resource is 250 meters and the coal inferred resource is 500 meters. Based on the estimation and classification with relative kriging standard deviation (RKSD), the total coal measured resource is 1.8 million tons, the coal indicated resource is 3.2 million tons and the coal inferred resource is 2.5 million tons with total coal resources.
Illegal artisanal and small-scale mining practices: re-thinking the harm
Authors: Agustina Putu P. S. , Herdiansyah Herdis , Harahap Anggi A. 
Published: July 2021

Abstract
Illegal and small-scale mining that occurs is often only seen as legal practices. Consequently, the government’s response towards it is more repressive ways, even negligent. This paper suggests another perspective in understanding these practices, especially in questioning who or what has been harmed, how and why it happened this way. Findings found that the concept of environment, including environmental damage, is a social construction that can be selected and filtered by the public, to determine which ones will be raised and become an important issue in the public. Although the detrimental effects of illegal mining are evident both socially and environmentally, there are social processes (interpretation and contestation) involved in determining the definition, scale, impact, and risk. Talking about why to this day illegal mining cases still occur and tend to be ignored is because basically the definition of environmental harm is a matter of social construction and is openly interpreted and contested by the definition.
MRT as an Alternative Transportation Solution which is environmentally friendly and traffic jam free in Jakarta
Authors: Ratnawati Elfrida 
Published: July 2021

Abstract
The ease, the existence of vacancies, Development of area, reducing pollution, and investment in Indonesia are some the benefits of the presence of Jakarta MRT in Indonesia. What is the role of MRT operations as a solution to traffic jam and air pollution in Jakarta? How does the presence of the MRT affect for the Jakarta citizens? And Is the MRT operating arrangement same as the train? The things mentioned above are the problems in this writing. The purpose of this paper is to describe the role of MRT operations as a solution to traffic jam, air pollution and the influence of the existence of the MRT to the Jakarta citizens in using public transportation. The research used is Normative with secondary data supported by primary data and analyzed descriptively through a qualitative approach. The role of the operation of the Jakarta MRT is very supportive in reducing air pollution. Its speed, capacity to accommodate a large number of passengers and reduce pollution are the role of the MRT as a solution offered by the government to reduce problems in Jakarta, namely traffic jam and air pollution. MRT is the same as the Train, which is the mode of land transportation but has a different legal basis, passenger capacity and operation.
Fish diversity monitoring in Maninjau Lake, West Sumatra using the eDNA with the next generation sequencing (NGS) technique
Authors: Roesma D I , Tjong D H , Janra M N , Aidil D R 
Published: July 2021

Abstract
Various phenomena in nature and human activities have resulted in the loss of biodiversity, such as freshwater fish in Maninjau lake, West Sumatra, which has declined from year to year. A new method to monitor biodiversity quickly and efficiently is the NGS technique on environment DNA (eDNA). The study aimed to know the NGS technique’s ability and effectiveness to detect multiple species at one time from the water samples of Maninjau Lake. Water was taken from the surface as much as one L with two replications. The sequencing was used to identify species as shotgun metagenomic with universal primers. The results showed that 92 individuals were identified with 56 species from 24 genera, 16 families, and 12 orders. As much as 25% of fishes still cannot be grouped into the valid taxa (unclassified), which is allegedly related to the lack of available information database (NCBI) compared to the sequences obtained. NGS on the eDNA method detected two families (Cyprinidae and Cichlidae), three genera (Oreochromis, Cyprinus, and Xiphophorus), and two species of fish (Oreochromis niloticus and Cyprinus carpio) in Maninjau Lake, which were also previously reported using the conventional method. The native species were not detected in Maninjau lake by the eDNA method allegedly due to not being captured DNA from the collected water samples or the low DNA concentration, which cannot be continued to the PCR process. Thus, several efforts are needed to reduce the limitations in monitoring using the eDNA method to obtain the maximal results. The eDNA method can be a useful tool for monitoring biodiversity. The result can determine the conservation strategies, especially for the fishes in Maninjau Lake, West Sumatra.
Quality of Fermented Purple Sweet Potato (Ipomea batatas var. Ayamurasaki) (Tapai) in Various Yeast Concentration and Steaming Time
Authors: Azara R , Qur’aini L , Saidi I A , Hudi L , Nurbaya S R , Budiandari R U 
Published: July 2021

Abstract
The aim of this work is to study the effect of yeast concentration and steaming time on the characteristics of fermented purple sweet potato (tapai). Experiment was conducted on completely randomized factorial design, with two treatments, namely yeast concentration (0.25%, 0.50%, and 0.75%) and steaming time (20 minutes, 30 minutes and 40 minutes). The measuring parameters was consisted physical properties (texture and color) and chemical proprerties (reducing sugar, ethanol content, total lactic acid, pH, and moisture content). The result show that yeast concentration treatment had a very significant effect on texture, total lactic acid, and pH. Steaming time had a very significant effect on texture, pH, and significantly affected the total lactic acid. In conclusions, the best treatment is obtained from the treatment of steaming time 30 minutes with 0.75 % yeast.