Journal of Hunan University Natural Sciences

Energy performance and surging dominate the life cycle cost of centrifugal gas compressors. To optimize compressor performance and reliability, the operating point on the compressor performance map is always set far from the surge control line. This results in significantly increased energy consumption owing to the backflow of compressed gas into the inlet pipes. This study presented the development of a novel and robust tool that enables real-time energy performance and surge monitoring of compressors. In the methodology, the off-design performance of the compressor was evaluated on the performance map provided by the OEM and design data. Microsoft Excel was used to digitize compressor performance maps, including surge curves, because it is easier and less expensive than other software, and users have constant access to source code updates. The results showed that the maximum compressing production gas for the 1^st stage was 2093.89m3/h, and 1413.53m3/h for the 2^nd stage. The polytropic head obtained 130kJ/kg for the low-pressure and 100kJ/kg for the high-pressure stage. While energy consumption was obtained at 5340kWh for the 1^st stage and 8000kWh for the 2^nd stage, when the compressor was running at full load with 8950 rpm with a 10% surge control line, it showed that the compressor was not surging. According to the findings, the compressor performance deviates from the designed conditions. Therefore, this monitoring tool assists operators and maintenance engineers in tracking the actual health performance of centrifugal compressors, predicting maintenance needs, and reducing maintenance costs and accidental equipment failures.

Keywords: predictive maintenance, surge control, energy performance, compressor.

https://doi.org/10.55463/issn.1674-2974.51.2.11

Elevated levels of environmental pollution, depletion of natural areas, and eradication of various forms of life have determined the impact of climate change. This phenomenon is affecting many countries with droughts, floods, wildfires, viruses, and pests, among other challenges. Conservation of the environment relies solely on human beings. Therefore, considering a quantitative approach, our objective was to determine how the ecotheater strategy enables students to enhance their anthropocentric and ecocentric environmental attitudes. We aimed to establish whether gender makes a difference and evaluate the level of understanding of socio-ecological systems achieved by students through their pictorial content in a population of 35 students. The results indicate that after the use of the ecotheater strategy, students significantly adopted ecocentric attitudes. Among the findings, the environmental dimension progressed the most in behavior change by students, reaching its maximum value. Additionally, the drawings allowed an understanding of the interrelationships between humans and living beings, placing them at level 4, reflecting respect for all forms of life and their reciprocal relationship with the environment. Finally, girls exhibited higher ecocentric behaviors than boys. The study suggests designing learning environments with ecotheater and outdoor activities to foster more reflective and situated attitudes of care and preservation of our environment with responsibility and ethics.

Keywords: ecocentrism, environmental awareness, drawings and explanations, ecological theater.

https://doi.org/10.55463/issn.1674-2974.51.2.10

Crime can occur anytime and anywhere, including on the way from the place of residence to the location of work, and vice versa. Approximately 75% of commuters in the Jabodetabek Metropolitan Area are private vehicle users, and 25% of commuters use public transportation modes. Regardless of the transportation mode used in their journeys, the probability of being a crime victim is unavoidable. Travel time is an important factor in determining the probability of becoming a crime victim. This study aims to analyze 1) the probability of becoming a crime victim while commuting in the Jabodetabek Metropolitan Area; 2) the impact of travel factors on the probability of becoming a crime victim while commuting in the Jabodetabek Metropolitan Area; and 3) the impact of individual factors on the probability of becoming a crime victim while commuting in the Jabodetabek Metropolitan Area. The novelty of this study is that the research is unobstructive as it analyzed existing data about the risk of a commuter becoming a crime victim. The existing statistical data used in this study are from Commuter Surveys in the Jabodetabek Metropolitan Areas 2019 microdata. This survey was conducted by the Central Bureau of Statistics in 2019 and is an important source of information for determining policies regarding commuting behavior and patterns in the Jabodetabek Metropolitan Area. Data exploration was based on commuters’ criminal experiences and their relation to travel time. This study also applies an alternative model in which other variables such as individual factors (gender, age, marital status, education, employment status) and travel factors (mode of transportation, distance travel, time of departure, time of arrival at home. Descriptive statistics analyze the data by using cross tabulation between the dependent variable (probability of being a crime victim) and each independent variable. The inferential analysis in this study uses logistic regression analysis by applying some alternative developed models.

Keywords: unobstructive research, travel time, logistic regression.

https://doi.org/10.55463/issn.1674-2974.51.2.9

This article describes the importance of emotional factors in the mathematics learning process. The research was conducted with first-semester engineering students from the Technological University of Pereira, and the topic addressed was complex numbers. This study aims to reveal the dynamics between cognition and emotion for an improvement in the mathematics learning process. Regarding the methodology, the guidelines provided by qualitative research were considered. With the support of grounded theory (TF), it contributes to the generation of new theories that arise due to observations that explain a social phenomenon in a natural and everyday context. The phenomenon that was observed and analyzed is the emotions that are generated in students when faced with the study of complex numbers. The sample was made up of 24 students, to whom collection instruments were applied to understand the emotional and conceptual aspects of the students. The results and conclusions describe the importance of the emotion– cognition relationship and the influence of didactic activities that generate positive emotions for the generation of lasting and significant learning. In addition, the relationship that the student can establish with the teacher is important in the sense that it gives them confidence to express what they feel and not feel embarrassed. How the teacher expresses himself toward the student and the invitation made to participate in class activities are considered a point of reference so that the student has confidence and tranquility during class and can develop the work with greater ease and security.

Keywords: emotion, learning, mathematics, student, teacher, didactics.

https://doi.org/10.55463/issn.1674-2974.51.2.8

Micro, small, and medium enterprises (MSMEs) advance the Indonesian economy. Being an alternative new job opportunity, MSMEs drive economic growth rate. In the Banyumas district, many MSMEs are starting, supported by government policies that are increasingly pro-MSMEs as a community economic activity to reduce poverty. Some MSMEs in Banyumas district are stuck and have difficulty developing after the COVID-19 pandemic. Many people are still hesitant about starting a business after the pandemic because many MSMEs closed during the pandemic. Lack of management capacity and inadequate technical skills caused the lack of development of MSMEs in Banyumas. Therefore, there is a need for research that looks at the comprehensive picture of the MSME industry in Banyumas district. This study aims to examine the industrial entrepreneurship model to increase MSME income industrially and the factors that influence it, including industrial entrepreneurship profile, resource variables, and innovation. The mediating variable used is production resource management. This research uses MSMEs' income variables and the factors influencing entrepreneurship and managing production resources. This study finds the novelty of production resource management as a highlight to increase the income of MSMEs. This research uses an analysis technique and the partial least squares structural equation modeling to examine the extent of the relationship among the variables. The result shows that industrial entrepreneurship and resource variables directly affect the income of MSMEs. Also, production resource management is a mediating variable for resource variables that affect MSMEs' income.

Keywords: MSME income, industrial entrepreneurship, resource, innovation, production resource management.

https://doi.org/10.55463/issn.1674-2974.51.2.7