Optimization of Technological Parameters when Plasma Nitriding the Gear Working Surface

This paper presents the results of optimizing the technological parameters when plasma nitriding the gear working surface. 27 experiments were carried out on an H4580 Eltrolab instrument to obtain a working surface hardness database table, and the Minitab statistical software was used to process the experimental results. A regression equation was identified to analyze the influence of temperature, time, and gas permeation concentration on the hardness of the working surface. An analysis of variance (ANOVA) showed that all these nitriding parameters influence the regression equation. The results showed that the permeation temperature TL has the greatest influence on the hardness, while the permeation time h and the first gas permeation concentration G1 had less influence. An optimal set of technological parameters was established, where the permeation temperature was TL=550°C, permeation time was h=8h, and the first gas permeation concentration was G1=4l/h. Experiments were carried out using this set of optimal parameters to evaluate the microstructure and the depth of the hardening layer of the part surface. Finally, this study presented the whole process for the permeation and plasma nitriding of 18XГT steel

Determinants of customer's apartment purchase intention: is the location dominant?

The purpose of this research is to identify and measure the factors affecting the intention to buy apartments of customers in Ho Chi Minh City, Vietnam. The survey carried out with the participation of 200 customers. The authors explore five factors which affect customer's apartment purchase intention include location, features, brand, finance, and subjective norm. The result from Exploratory Factor Analysis (EFA) shows that location, features, finance, and subjective norm have a significant effect on the intention to buy customers' apartments. In which, location in Ho Chi Minh City context is the most influential factor, so, it strongly confirm the research of Adair et al. (1996), Clark et al. (2006), Daly et al. (2003), Kaynak and Stevenson (2007), Opoku and AbdulMuhmin (2010), Sengul et al. (2010), Tu and Goldfinch (1996), Xiao and Tan (2007) and Wang and Li (2006). The study also proposes some recommendations to increase the attractiveness of the apartment. What is more, developers, marketers, real estate policymakers can use the results of this research to understand the needs of customers better and satisfy customers

A new species of the genus Halicyclops (Copepoda, Cyclopoida, Cyclopidae) from freshwater in Central Vietnam

A new cyclopoid species belonging to the genus Halicyclops, H. songsonensis sp. nov. is described from freshwater in Son river, Quang Binh province, Central Vietnam. The new species is distinguished from the other congeners species of the genus by a combination of the having 3:4:4:3 spine formula on P1-P4, lateral angular protuberances on the genital double-somite, a serrate hyaline frill of pre-anal somite little more developed than lateral and ventral parts, relatively long caudal rami, spiniform seta of proximalmost seta on P2-P3 Enp3 and showing the round/oval integumental window on cephalothorax and two next prosomites

Fuel injection responses and particulate emissions of a crdi engine fueled with cocos nucifera biodiesel

The objective of this paper is to study the effect of coconut oil biodiesel (COB)-diesel blends on exhaust particulate matter (PM) emissions and fuel injection responses in an unmodified turbocharged four-stroke common-rail direct injection (CRDI) diesel engine. Characterization of COB and their blends has been conducted to ascertain the applicability of these fuels for the existing engine. The test fuels used were fossil diesel fuel, COB10, COB20, COB30 and COB50 of biodiesel-diesel fuels. A test cycle which composed of 16 different steady-state modes at various loads and speed conditions was followed. Generally, the results showed a marginally advanced SOI timing and longer injection duration with increasing COB blends at higher load as compared to diesel fuel. Additionally, the lower calorific value (CV) and higher viscosity of the COB fuel blends have resulted in reduced turbo boost pressure and increased common-rail fuel injection pressure, respectively, across all engine speeds and loads. On the aspects of PM emissions characterization, results indicated that the blending of COB with conventional diesel had benefits over diesel in PM reduction. In fact, the largest achievable PM mass reduction of 38.55% was attained with COB50. In addition, it was noticed that the size of PM particles accumulated such that the granular size increased with higher diesel content in the blend. Additionally, the composition analysis on the PM collected by EDX spectroscopy has revealed that the C, O and Si as three main elements that made up the PM particles in descending order. Overall, the results indicated that COB biodiesel is a clean-burning alternative fuel and can be used satisfactorily in an unmodified diesel engine without the needs for engine remapping

Numerical simulation of all-normal dispersion visible to near-infrared supercontinuum generation in photonic crystal fibers with core filled chloroform

This study proposes a photonic crystal fiber made of fused silica glass, with the core infiltrated with chloroform as a new source of supercontinuum (SC) spectrum. We numerically study the guiding properties of the fiber structure in terms of characteristic dispersion and mode area of the fundamental mode. Based on the results, we optimized the structural geometries of the CHCl3-core photonic crystal fiber to support the broadband SC generations. The fiber structure with a lattice constant of 1 μm, a filling factor of 0.8, and the diameter of the first-ring air holes equaling 0.5 μm operates in all-normal dispersion. The SC with a broadened spectral bandwidth of 0.64 to 1.80 μm is formed by using a pump pulse with a wavelength of 850 nm, 120 fs duration, and power of 0.833 kW. That fiber would be a good candidate for all-fiber SC sources as cost-effective alternative to glass core fibers

The Relationship Between Corporate Social Responsibility and Employee Organizational Commitment in Multinational Corporations in Ho Chi Minh City

Based on the theoretical background of previous studies and the increasing context of personnel turnover in multinational companies, the authors conduct this study with the research objective to test and measure the impact of Corporate Social Responsibility (CSR) on employee’s organizational commitment through the effect of organizational identification and organizational trust. The combined qualitative and quantitative research methods were used to process and analyse the data. Research data was collected from 271 employees working in multinational corporations in Ho Chi Minh City. The study also discusses and provides some governance implications to help MNCs improve their social responsibility towards social and non-social stakeholders, employees, customers and the government as well as increase employee organizational engagement through identification and trust in the organization. Keywords: corporate social responsibility, employee organizational commitment, organizational identification, organizational trus

Optimization of fuel injection parameters of moringa oleifera biodiesel-diesel blend for engine-out-responses improvements

Biodiesel has gained popularity in diesel engines as a result of the rapid decline of fossil fuels and population growth. The processing of biodiesel from non-edible Moringa Oleifera was investigated using a single-step transesterification technique. Both fuels had their key physicochemical properties measured and investigated. In a common-rail diesel engine, the effects of MB50 fuel blend on the symmetric characteristics of engine-out responses were evaluated under five load settings and at 1000 rpm. As compared to standard diesel, MB50 increased brake thermal efficiency (BTE), and nitrogen oxides (NOx) emissions while lowering brake specific fuel consumption (BSFC), and smoke emissions for all engine loads. A further study of injection pressure and start of injection (SOI) timing for MB50 fuel was optimized using response surface methodology (RSM). The RSM optimization resulted in improved combustion dynamics due to symmetry operating parameters, resulting in a simultaneous decrease in NOx and smoke emissions without sacrificing BTE. RSM is an efficient optimization method for achieving optimal fuel injection parameter settings, as can be deduced. As a result, a clearer understanding of the use of MB50 fuel in diesel engines can be given, allowing for the best possible engine efficiency

Experiment and FEM Modelling of Bond Behaviors between Pre-stressing Strands and Ultra–High–Performance Concrete

The objective of this paper is to investigate the bond properties of prestressing strands embedded in Ultra–High–Performance Concrete (UHPC).The UHPC was made in laboratory using local materials in Vietnam.Its mixture contains: silica aggregates, portland cement PC40, fly ash, silica fume, polycarboxylate superplasticizer and the micro steel fibers.The experimental process is realized on a pull-out test. The volume fraction of micro steel fibers in UHPC was 2%. The prestressing strand with diameters of 15.2mm was considered. The interface shear strength between strand and UHPC is identified based on the results of force and displacement obtained during the pull-out test. The Cohesive Zone Model (CZM) is implemented in finite element model to study this interface behavior. This model described by a piecewise linear elastic law. The CZM’s parameters are identified based on experimental results of pull-out test.The numerical studies are used the CZM in ANSYS software. Two numerical tests are realized and compared with experimental results: pull-out test and other test to verify the deflection of I girder due to prestressing force

Experiment and FEM Modelling of Bond Behaviors between Pre-stressing Strands and Ultra–High–Performance Concrete

The objective of this paper is to investigate the bond properties of prestressing strands embedded in Ultra–High–Performance Concrete (UHPC).The UHPC was made in laboratory using local materials in Vietnam.Its mixture contains: silica aggregates, portland cement PC40, fly ash, silica fume, polycarboxylate superplasticizer and the micro steel fibers.The experimental process is realized on a pull-out test. The volume fraction of micro steel fibers in UHPC was 2%. The prestressing strand with diameters of 15.2mm was considered. The interface shear strength between strand and UHPC is identified based on the results of force and displacement obtained during the pull-out test. The Cohesive Zone Model (CZM) is implemented in finite element model to study this interface behavior. This model described by a piecewise linear elastic law. The CZM’s parameters are identified based on experimental results of pull-out test.The numerical studies are used the CZM in ANSYS software. Two numerical tests are realized and compared with experimental results: pull-out test and other test to verify the deflection of I girder due to prestressing force