bluuebunny/crossref_metadata_2025_split huggingface dataset:
Guided inquiry model based on scientific approach to science learning of the students of SMPK Stella Maris Biudukfoho
Authors: Tabun Y F , Sunarno W , Sukarmin  
Published: September 2019

Abstract
This study aimed to determine the science learning outcomes of students in the aspect of cognitive, affective and psychomotor using a guided inquiry model based on a scientific approach. This study is quasi-experiment with nonequivalent control group design. The population is the whole students of Stella Maris Biudukfoho Chatolic Junior High School (SMPK) at grade eight in the Academic Year of 2018/2019. The sample consists of two classes taken by cluster random sampling technique, namely class VIII A as the experimental class and class VIII B as the control class. Data collecting tools namely tests, questionnaires and observation sheets were used in this study. Data analysis of students’ learning outcomes were done using Independent Samples t-test. The results of the three aspects of learning outcomes namely aspects of knowledge, attitudes and skills indicated that the p-value < 0.05 so that H0 is rejected and Ha is accepted. Thus, there were differences in learning outcomes of students who were given learning method using guided inquiry with students using who were given conventional learning. However, the results from data analysis, p-value of knowledge aspect is 0.000, p-value of attitudes aspect is 0.043 and p-value of skills aspects is 0.001.
Influence of physics problem-solving ability through the project based learning towards vocational high school students’ learning outcomes
Authors: Retno N H D , Sunarno W , Marzuki A 
Published: September 2019

Abstract
Physics, an adaptive subject in SMK, is the basis and prerequisite for productive and applicable material, so it needs to be emphasized on problem solving approaches. This study aimed to determine the influence of learning methods based on the problem solving ability on learning outcomes. The intended learning outcomes are cognitive learning outcomes and the learning method used is project based learning. The type of research was quasi-experiment. The population in this study were the 10th grade students of SMK Negeri 5 Surakarta in the 2018/2019 academic year which consisted of 7 majors with 22 classes. The sample of this study were 2 classes from the Mechanical Engineering department, each of which amounted to 35 students. The instrument used in this study consist of 20 multiple choice questions and 5 essay question of the Physics problem solving abilities. Data were analysed using normality test, homogeneity test and hypothesis testing with analysis of variance techniques (ANOVA). Based on the results of the study it was found that the influence of the interaction between learning method and problem solving ability on cognitive learning outcomes showed sig 0.043 ≤ 0.05. It can thus be concluded that there was an influence of the interaction of the learning model with the problem solving ability with cognitive learning outcomes. Therefore project based learning methods can be used as an alternative for teachers in carrying out their learning to create an active learning atmosphere and enhance students’ ability to understand physics problems.
Fractionation and determination of phenolic and flavonoid compound from Moringa oleifera leaves
Authors: Martono Y , Yanuarsih F F , Aminu N R , Muninggar J 
Published: September 2019

AbstractMoringa oleiferais one of the nutrient-dense multipurpose plants that grows in Indonesia.M. oleiferaleaf extract contains many phenolic compounds and flavonoids, one of them is quercetin compounds. In this study, total phenolic, total flavonoid, and quercetin compounds were determined based on their fraction as free phenolic acids (FPA), phenolic acid ester (PAE), and phenolic acid glycosides (PAG) which separated by phenolic acid fractionation methods. Fractionation method was done by liquid-liquid extraction. Total Phenolic compounds and flavonoid were determined using spectrophotometric UV-Vis. The concentration of quercetin was determined using High-Performance Liquid Chromatography (HPLC). Total phenolics in the crude extract (CE), FPA, PAE, and PAG fractions respectively were 50.2042; 5.7963; 1.5260; and 0.0617 mg/g GAE. The total flavonoids in the CE, FPA, PAE, and PAG fractions were 25.6627; 1.7207; 1.0510; and 0.2843 mg/g QE. The quercetin compounds in the CE, FPA, PAE, and PAG fractions were 1.7123; 1.9607; 0.1921; and 0.5067 μg/g.Moringa oleiferais potential natural sources for phenolic and flavonoid, particularly of quercetin.
Analyzing the shape of photoacoustic signal on audible frequency modulation
Authors: Setiawan A , Rondonuwu F S , Setiaji F D 
Published: September 2019

Abstract
This paper reports the result of measurement and analysis of the shape of photoacoustic signal emitted from an object which is a piece of carbon paper, excited by a diode laser beam, which modulated by a square wave signal at audible frequency, so that acoustic measurement can be done easily and inexpensive. Here PC Real Time Audio Spectrum Analyser (RTA 168) from Virtins Technology is used to measure and record the acoustic signal. Three modulation frequencies were chosen which were 5.045, 9.576 and 14.816 Hz, all with 50% of duty cycle. The result showed that the fundamental frequency of photoacoustic signal fit to modulated laser’s signal. Measurement at 5,045Hz, as an example, showed that the shape of the photoacoustic signal fit to the model with average error of 5%. The absorbtion coefficient of carbon paper could also be calculated as μa
=1.49cm−1.
Shear Strength Characteristics of Coastal Soil Treated with Sodium Silicate
Authors: Erica Amaludin Adriana , Teo Twan Ann Melvin , Radzif Taharin Mohammad , Dullah Salinah 
Published: September 2019

Abstract
In recent times, rapid developments near coastal areas are gaining attraction and attention from industry players. This necessitates further understanding of soil behavior found in these areas. Soil stabilization can further enhance the physical and engineering characteristics of soils used for development purposes. For this study, a series of laboratory tests were conducted to determine the potential of Sodium Silicate (TX-85), a liquid-type chemical soil stabilizer, to improve the properties of coastal soil obtained in Kota Kinabalu, Sabah. The soil samples were subjected to a series of laboratory tests, which includes the pH and Unconfined Compression Strength (UCS). The dosages of Sodium Silicate mixed with the soil were 4, 5, and 7% by soil sample weight, with curing intervals of 3 hours, 24 hours and 48 hours, respectively. The optimal dosage of Sodium Silicate observed in this study is 4%, at 48 hours curing period. This combination of stabilizer dosage and curing period produced the highest strength increment, where the UCS value increased by 90.3%, from 262.1 kPa to 498.8 kPa.
Dimensions of Tenants’ Office Leasing Behaviours: An Introductory Study
Authors: Kim Sumin , Lim Benson T.H. 
Published: September 2019

Abstract
The greenness of office buildings is becoming a more important issue as it contributes to the sustainability of the building sector. Moreover, by leasing greener offices, tenants can be benefitted by the improved indoor environmental quality and better corporate branding attributed to its positive image. These benefits, however, often come with relatively expensive prices that tenants need to pay. Nevertheless, the sources of the price premium have not been fully explored especially from the aspect of tenants’ leasing behaviours. To address this, a questionnaire survey was conducted. Then, exploratory and confirmatory factor analysis were performed to identify the underlying dimensions of tenants’ leasing behaviours and to ensure their reliability and validity. The results show that tenants’ office leasing behaviours must be explained by several dimensions. Also, it is found that the obtained results have a sufficient reliability and validity. These allow proceeding to the next stage of the research to explain if and to what extent the greenness level of tenants’ offices and the rents they pay are influenced by various motivational variables based on the established analytical model.
Conceptualising eco-innovation practices in contractor firms – the dynamic capability approaches
Authors: Sarah Mat Isa Siti , Zainul Abidin Nazirah , Yahaya Izyan 
Published: September 2019

AbstractThe world has witnessed extreme environmental deterioration over the past few decades due to rapid development in urban areas and unsustainable way of past construction. Recently, eco-innovation (EI) has increasingly been accepted as the solution to major environmental problems. EI involves new or modified processes, techniques, products, systems, and services that can satisfy human needs and provide quality of life whilst significantly decreases environmental impacts. In addition, EI revolutionary path to improve contractor firms’ competitiveness and sustaining business endeavour. Thus, the aim of this paper is to develop EI framework practices in contractor firms. Unfortunately, to be eco-innovative, the contractor firms need to strengthen their green knowledge, technology and resources as well as to develop their capabilities and strategies faster than their rivals. They also need to absorb and capitalise any external opportunities for their own advantages. Therefore, this study adopts dynamic capability theory to investigate a firm’s ability to integrate, build and reconfigure its competences and resources to accomplish the environmental goal in its business strategy. The outcome of this paper could provide clear directions of EI practices by means of dynamic capability theory in demonstrating how contractor firms can adapt to changing current industry conditions to remain competitive.
Compressive Strength and Infiltration Characteristic of Pervious Concrete Using Recycled Concrete Aggregate
Authors: Aishah Abd Rahman Nurul , Aiman Muhamad Shah Muhammad , Safwan Muhamad Noor , Amzari Yaccob Ahmad , Zardasti Libriati 
Published: September 2019

Abstract
In construction industry, rapid development will increase the demand versus supply which leads to increasing the production of construction waste. Recycle Concrete Aggregate (RCA) was proposed as the one of the component in the pervious concrete for sustainability in the construction industry to reduce the wastage. The pervious concrete was function as a medium to allow the water penetrate through porosity of the concrete and avoiding water from pooling at the surface. Therefore, this study is conducted to investigate the properties of the pervious concrete by infiltration test and compression strength test using Recycle Concrete Aggregate (RCA) and Natural Aggregate (NA) as the main composition. The cement aggregate ratio of 1:3 and 1:5 were choosing as variable to produce the workability pervious concrete that similar to conventional concrete. The replacement of NA with RCA is likely a viable option for structural use.
Screw Rotors with Partial Length Contact.
Authors: Davey D W 
Published: September 2019

Abstract
Tribology theory suggests manufacturing screw rotors with partial helical contact along the longitudinal axis of the intermeshing rotors may significantly influence their lubrication characteristics. This paper considers the theoretical effects of using this geometry feature for multiphase flow machines. Modelling of machines that include partial contact along with other relevant aspects such as oil port location, has further been investigated using ANSYS CFX and some results of these simulations are presented and discussed.
Analysis of rolling bearing power loss models for twin screw oil injected compressor
Authors: Abdan S , Stosic N , Kovacevic A , Smith I , Asati N 
Published: September 2019

Abstract
The mechanical losses inside a screw compressor limit the performance of the compressor in terms of efficiency. These losses arise due to relative motion between elements inside the screw compressor. The estimation of mechanical losses predicted in the literature is around 10-15% of the total shaft power. One of the elements which contribute significantly to these losses is rolling element bearings. There are numerous mathematical models available which predict power losses in the rolling bearings.
The objective of this paper is to study different models to predict power loss for rolling bearings and to predict the power losses for the bearings used for oil injected, twin screw compressor. A comparison between different power loss models for different operating conditions of compressor is also presented in this paper and results of analysis are compared with available experimental observations. The analysis helps to determine suitable power loss model for different operating conditions and more realistic predictions of the power losses. This allows designers for more accurate estimation of the performance of screw compressors.
Experimental Investigation of a Mechanically Assisted Suction Reed Valve in a Small Hermetic Reciprocating Compressor
Authors: Egger A , Almbauer R , Dür L , Hopfgartner J , Zuber B , Stangl S 
Published: September 2019

Abstract
Reed valves are widely used in hermetic reciprocating compressors and are responsible for a major share of thermodynamic losses. In particular, the suction valve movement of a hermetic reciprocating compressor contains a potential for further improvement. The self-actuated valve is opened only by the pressure difference created by the moving piston, which leads to a characteristic flutter. Furthermore, the suction valve is usually preloaded in order to close properly before the compression phase, causing additional flow resistance.
In this work a mechanically assisted suction valve is experimentally investigated. A mechanically actuated spring element generates an additional force acting on the conventional suction reed valve. This force leads to a completely different valve motion. While a conventional reed valve motion is characterized by several opening-and closing periods during one suction phase, the mechanically assisted valve remains open during the whole suction phase. Furthermore, the maximum impact velocity of the valve can be reduced significantly. Thus, not only the suction losses but also the valve stress can be reduced.
To investigate the mechanically assisted suction valve, a conventional small capacity hermetic reciprocating compressor is fitted with measurement equipment and additional components for the mechanical valve actuation. Preliminary investigations are made without the hermetic shell to find an appropriate design. Finally, measurement results of the compressor running at steady-state conditions on a calorimeter test bench (R600a) show significant improvements of the coefficient of performance (COP) at different rotational speeds and operating conditions.
Outsourcing in the Compressed Air Sector – Financial Opportunities in Industry
Authors: Vittorini Diego , Cipollone Roberto 
Published: September 2019

Abstract
The compressed air sector is currently responsible for up to 10% world-wide overall industry electricity consumption, 30% of which ascribable to the compressor technology alone. Such a datum makes the saving potential from a proper compressor selection (30-35% overall consumption) as appealing as those associated with other energy measures and in line with the 20-20-20 timeline. Plus, every electricity saving on the compressor virtually corresponds to an income from selling Energy Saving Certificates (usually referenced as White Certificates) and CO2 quotas from avoided emissions on dedicated markets, which can eventually reduce the payback time of the additional investment. Outsourcing in the CAS is addressed as the most effective alternative to efficiency ownership and its development is supported by the common perception of the compressed air as a utility, analogously to electricity and thermal energy. An in-depth net present value analysis is performed on market compressors for industrial purposes, based on the environmental market model, the electricity cost and compressors market policy in the average European context. In addition to the financial advantage from White Certificates and Carbon markets, the outsourcing always benefits from the lower investment cost on the compressor and the higher compressors efficiency: this results in lower sale prices for the cubic meter of compressed air, with little or no difference among different machine types. The relative importance of energy and investment-related costs is assessed as well. The outsourcing allows a m3 cost reduction with respect to the purchase of new compressors in the 15-20% range, dependently on the machine size and operation regime.
Characterization of wire mesh structure for coalescing oil separation
Authors: Xu Jiu , Hrnjak Pega 
Published: September 2019

Abstract
Oil separation is commonly needed in air conditioning or refrigeration systems to reduce the oil circulation rate and keep the oil inside the compressor. For compactness, the oil separation structure integrated into the compressor is more and more popular than traditional external oil separator. This paper presents coalescence, one of the basic mechanisms of droplet separation, studied by quantitative flow visualization and measurements. The misty oil flow through separator is visualized by a high-speed camera and analyzed quantitatively. Oil droplet size and its distribution are determined by video processing. Important flow details are revealed, including oil droplet collision, oil droplet coalescence, oil film breakup and re-entrainment. Separation efficiency is determined as the ratio between drained and incoming oil mass flow rate. Pressure drop is also measured since it is a cost due to separation structures.
Optimization of a three spool axial compressor to increase the efficiency of a gas turbine engine
Authors: Marchukov Evgenii , Egorov Igor , Popov Grigorii , Baturin Oleg , Goriachkin Evgenii , Novikova Yulia 
Published: September 2019

Abstract
The paper provides a description of the algorithm, an example of a specific task, and the results of the optimization of a 15-stage three-spool compressor for a ground-based GTU by the efficiency criteria of the engine. It can be performed by using the proposed algorithm to find such a compressor configuration that will be not just the optimum compressor, but the best option for working as part of the engine under the specified operating conditions and with various types of required restrictions. Using the proposed algorithm, varying only the stagger angles of the profiles, the authors managed to find a way to increase the overall efficiency of the NK-36ST engine by 0.43%. Obviously, it is possible to achieve a more impressive result and at the same time to increase reliability, reduce the weight and cost of the engine by applying more complex models by changing the shape of the blade profiles.
Control and Commissioning of a Hot Gas Bypass Compressor Load Stand for Testing Light-Commercial Compressors on Low-GWP Refrigerants
Authors: Singleton Jake , Schmidt Drew , Bradshaw Craig R. 
Published: September 2019

Abstract
Because of changing efficiency standards for HVAC&R equipment, hydrofluorocar-bon refrigerants such as R134a and R410A are in the process of being phased out because of their high Global Warming Potential (GWP). Many low-GWP refrigerants, such as R1234yf, R1234ze(E), R1234ze(D), R32, and several blends of these, are being considered as replace-ments. This creates a need for design changes to compressors. Recent work by Schmidt et al. (2018) presented a hot-gas bypass compressor load stand constructed at Oklahoma State University to facilitate testing of compressors with their new design changes.
The load stand has a design capacity range of 10-80 tons. This wide spectrum of testing conditions necessitates a comprehensive controls package to maintain stability and control over the simulated operating condition. This controls package was designed in LabVIEW and allows independent control over the compressor suction pressure and temperature and the discharge pressure using PI controllers. The controllers operate to both set the desired operating condition as well as minimize the variation of the parameters with time (i.e. random uncertainty).
A series of commissioning tests were performed to validate the stand operation and performance metric measurements using a 40 ton scroll compressor. The initial results suggested that appropriately balanced cooling water flow and appropriately tuned controllers are critical to minimize random uncertainty of the data. Without appropriate tuning or cooling water control the load stand was unstable. Adjusting the water flow provided stability but yielded random uncertainty of 0.014% compared with both water control and appropriately tuned controller which yielded random uncertainty of 0.0041%.
A new non-destructive method for fault diagnosis of reciprocating compressor by measuring the piston rod strain
Authors: Li Xueying , Peng Xueyuan 
Published: September 2019

Abstract
As an established method to analyse the thermodynamic process inside the cylinder, the p-V diagram can identify typical faults such as leakages through the sealing rings and self-acting valves, loosening and fluttering of the vales, etc. However, the installation of the pressure sensor within the cylinder for recording the p-V diagram may lead to degradation of the cylinder integrity, and hereby potential leakage and lowered strength of the cylinder. This paper presents a new non-destructive method for fault diagnosis of the reciprocating compressor by measuring the piston rod strain, from which the p-V diagram was transformed. An algorithm for reconstruction of the p-V diagram was proposed based on the key feature points on the piston rod load curve that reflect the opening and closing events of the compressor valves. The reconstruction method was validated by comparing the calculated p-V diagrams with the experimental results. The reconstructed p-V diagrams were further used for fault diagnosis of the reciprocating compressors, with which the acoustic emission method was integrated. The results show that this method can easily monitor the working conditions and identify whether and where leakage, fluttering and delayed closing of the valves occur, which indicates that this method can be utilized as a powerful tool of non-destructive condition monitoring and fault diagnosis of the reciprocating compressors.
Assessment of simplifying hypotheses adopted for valve leakage modeling
Authors: De Luca L G M , Silva E , Deschamps C J 
Published: September 2019

Abstract
The reed-type valves employed in refrigeration compressors must provide adequate sealing when closed to avoid leakage of gas between the compression chamber and the suction and discharge chambers. Recent studies show that valve leakage can considerably affect the performance of the small reciprocating compressors used for domestic refrigeration. The present paper reports an investigation on the adequacy of simplifying the hypothesis adopted in the simulation models of valve leakage. The results indicate that the transient effects related to both the valve deflection and fluid flow are negligible. Also, the ideal gas formulation was found suitable in some operating conditions found in domestic refrigeration. On the other hand, leakage was found to be overpredicted by almost 20% when the reed valve geometry was simplified to a circular plate in order to reduce the computational processing cost.