Youngkeun Choi and Jae Won Choi
Job involvement can be linked with important work outcomes. One way for organizations to increase job involvement is to use machine learning technology to predict employees’ job…
Abstract
Purpose
Job involvement can be linked with important work outcomes. One way for organizations to increase job involvement is to use machine learning technology to predict employees’ job involvement, so that their leaders of human resource (HR) management can take proactive measures or plan succession for preservation. This paper aims to develop a reliable job involvement prediction model using machine learning technique.
Design/methodology/approach
This study used the data set, which is available at International Business Machines (IBM) Watson Analytics in IBM community and applied a generalized linear model (GLM) including linear regression and binomial classification. This study essentially had two primary approaches. First, this paper intends to understand the role of variables in job involvement prediction modeling better. Second, the study seeks to evaluate the predictive performance of GLM including linear regression and binomial classification.
Findings
In these results, first, employees’ job involvement with a lot of individual factors can be predicted. Second, for each model, this model showed the outstanding predictive performance.
Practical implications
The pre-access and modeling methodology used in this paper can be viewed as a roadmap for the reader to follow the steps taken in this study and to apply procedures to identify the causes of many other HR management problems.
Originality/value
This paper is the first one to attempt to come up with the best-performing model for predicting job involvement based on a limited set of features including employees’ demographics using machine learning technique.
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Morteza Vatani and Jae-Won Choi
This work aims to present a guideline for ink development used in extrusion-based direct-write (DW) (also referred to as direct-print [DP]) technique and combine the extrusion…
Abstract
Purpose
This work aims to present a guideline for ink development used in extrusion-based direct-write (DW) (also referred to as direct-print [DP]) technique and combine the extrusion with instant photopolymerization to present a solvent-free DP photopolymerization (DPP) method to fill the gap between 3D printing and printing multi-functional 3D structures.
Design/methodology/approach
A DP process called DPP was developed by integration of a screw-driven micro-dispenser into XYZ translation stages. The process was equipped with direct photopolymerization to facilitate the creation of 3D structures. The required characteristics of inks used in this technique were simulated through dispersion of fumed silica particles into photocurable resins to transform them into viscoelastic inks. The characterization method of these inks and the required level of shear thinning and thixotropic properties is presented.
Findings
Shear thinning and thixotropic properties are necessary components of the inks used in DPP process and other DP techniques. These properties are desirable to facilitate printing and filament shape retention. Extrusion of viscoelastic inks out of a nozzle generates a filament capable of retaining its geometry. Likewise, instant photopolymerization of the dispensed filaments prevents deformation due to the weight of filaments or accumulated weight of layers.
Originality/value
The DPP process with material-reforming methods has been shown, where there remain many shortcomings in realizing a DP-based 3D printing process with instant photopolymerization in existing literature, as well as a standard guideline and material requirements. The suggested method can be extended to develop a new commercial 3D printing system and printable inks to create various functional 3D structures including sensors, actuators and electronics, where nanoparticles are involved for their functionalities. Particularly, an original contribution to the determination of a rheological property of an ink is provided.
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Hochan Kim, Jae‐Won Choi and Ryan Wicker
To operate a multiple material stereolithography (MMSL) system, a material build schedule is required. The purpose of this paper is to describe a scheduling and process‐planning…
Abstract
Purpose
To operate a multiple material stereolithography (MMSL) system, a material build schedule is required. The purpose of this paper is to describe a scheduling and process‐planning software system developed for MMSL and designed to minimize the number of material changeovers by using low‐viscosity resins that do not require sweeping.
Design/methodology/approach
This paper employs the concept of using low‐viscosity resins that do not require sweeping to minimize the number of material changeovers required in MMSL fabrication. A scheduling and process‐planning software system specific to MMSL is introduced that implements four simple rules. Two rules are used to select the material to be built in the current layer, and two rules are used to determine at which layer a material changeover is required. The schedule for the material to be built depends on the material properties stored in a user‐defined materials library. The developed algorithm produces sliced loop data for each material using the predetermined layer thickness from an input CAD model, and the four rules are applied at each layer. The algorithm then determines the build order for each material, the material‐specific number of layers to be built, and whether or not sweeping is required. Output data from the program are the scheduling and process‐planning report and the partitioned computer‐aided design models to be built before changing a material according to the process planning. Two examples of the algorithm applied to multiple material parts are provided.
Findings
The MMSL scheduling and process‐planning software system is developed using Microsoft Visual C++7.0. For verification, a simple demonstration is conducted on a two material part where the process plan could be easily determined through intuition. A more complex multiple material part is also tested that consisted of four subparts. Several cases of resin assignment are tested showing that the ultimate scheduling and process planning vary significantly depending on the material combinations and specifications. These examples demonstrate that the strategy, method, and software developed in this paper can be successfully applied to prepare for MMSL fabrication.
Research limitations/implications
Although the software system is demonstrated on two multiple material parts, more extensive work will be performed in the future on fabricating multiple material parts using the MMSL machine. It is expected that additional rules will be developed as additional limitations of MMSL are identified. It is also anticipated that particular emphasis will be placed on building without sweeping as well as development of advanced non‐contact recoating processes.
Originality/value
As designs incorporating multiple materials increase in the future and additive manufacturing (AM) technologies advance in both building out of multiple materials and fabricating production parts, the scheduling and process‐planning concepts presented here can be applied to virtually any AM technology.
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Jae‐Won Choi, Ryan B. Wicker, Seok‐Hyun Cho, Chang‐Sik Ha and Seok‐Hee Lee
The paper's aim is to explore a method using light absorption for improving manufacturing of complex, three‐dimensional (3D) micro‐parts with a previously developed dynamic mask…
Abstract
Purpose
The paper's aim is to explore a method using light absorption for improving manufacturing of complex, three‐dimensional (3D) micro‐parts with a previously developed dynamic mask projection microstereolithography (MSL) system. A common issue with stereolithography systems and especially important in MSL is uncontrolled penetration of the ultraviolet light source into the photocrosslinkable resin when fabricating down‐facing surfaces. To accurately fabricate complex 3D parts with down‐facing surfaces, a chemical light absorber, Tinuvin 327™ was mixed in different concentrations into an acrylate‐based photocurable resin, and the solutions were tested for cure depths and successful micro‐part fabrication.
Design/methodology/approach
Tinuvin 327 was selected as the light absorber based on its high absorption characteristics (∼0.4) at 365 nm (the filtered light wavelength used in the MSL system). Four concentrations of Tinuvin 327 in resin were used (0.00, 0.05, 0.10, and 0.15 percent (w/w)), and cure depth experiments were performed. To investigate the effects of different concentrations of Tinuvin 327 on complex 3D microstructure fabrication, several microstructures with overhanging features such as a fan and spring were fabricated.
Findings
Results showed that higher concentrations of Tinuvin 327 reduced penetration depths and thus cure depths. For the resin with 0.15 percent (w/w) of the Tinuvin 327, a cure depth of ∼30 μm was achieved as compared to ∼200 μm without the light absorber. The four resin solutions were used to fabricate complex 3D microstructures, and different concentrations of Tinuvin 327 at a given irradiance and exposure energy were required for successful fabrication depending on the geometry of the micro‐part (concentrations of 0.05 and 0.1 percent (w/w) provided the most accurate builds for the fan and spring, respectively).
Research limitations/implications
Although two different concentrations of light absorber in solution were required to demonstrate successful fabrication for two different micro‐part geometries (a fan and spring), the experiments were performed using a single irradiance and exposure energy. A single solution with the light absorber could have possibly been used to fabricate these micro‐parts by varying irradiance and/or exposure energy, although the effects of varying these parameters on geometric accuracy, mechanical strength, overall manufacturing time, and other variables were not explored.
Originality/value
This work systematically investigated 3D microstructure fabrication using different concentrations of a light absorber in solution, and demonstrated that different light absorption characteristics were required for different down‐facing micro‐features.
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Jae‐Won Choi, Rolando Quintana and Ryan B. Wicker
The objective of this paper is to demonstrate a method for producing embedded horizontal micro‐channels using a commercial line‐scan stereolithography (SL) system. To demonstrate…
Abstract
Purpose
The objective of this paper is to demonstrate a method for producing embedded horizontal micro‐channels using a commercial line‐scan stereolithography (SL) system. To demonstrate that the method is repeatable, reproducible and capable of producing accurate horizontal micro‐channels, a statistical design of experiments was performed.
Design/methodology/approach
Demonstration of the technique was performed using a 3D Systems Viper si2TM SL system and DSM Somos® WaterShedTM resin with polytetrafluoroethylene (PTFE)‐coated wire having diameters of 31.6 and 57.2 μm. By embedding the wire and building around the insert, the down‐facing surfaces were supported during fabrication enabling accurate fabrication of embedded micro‐channel geometries. The fabrication method involved first building an open micro‐channel, interrupting the SL process and inserting the wire, and then capping over the wire with multiple layers. After fabrication, the part with the inserted micro‐wire was post‐cured to harden any uncured resin around the wire. The micro‐channel was produced by simply pulling the wire out of the part. Scanning electron microscope images were used to examine and measure the geometries of the fabricated micro‐channels, and characterization through a statistical analysis was accomplished to show that the process was capable of producing accurate horizontal micro‐channels.
Findings
The measured data showed that the micro‐wires were successfully removed from the channels, leaving high quality micro‐channels, where the mean measured diameters for each wire were 2.65 and 2.18 μm smaller than the measured wire diameters (31.6 and 57.2 μm). Based on the statistical results, it is suggested that the method described in this work can rapidly produce repeatable and reproducible circular, embedded, and accurate micro‐channels.
Research limitations/implications
The method developed in the current work was demonstrated on simple straight channels and a statistical study was used to show that the process is capable of repeatedly and reproducibly producing accurate micro‐channels with circular cross‐section; however, future studies are required to extend these procedures to more realistic and complicated geometries that may include non‐straight channel paths and non‐circular cross‐sectional geometries. The process can be used for micro‐channel fabrication with not only circular cross‐sectional geometries as shown here but potentially with a wide range of additional cross‐sectional geometries that can be fabricated into a PTFE‐coated micro‐wire.
Originality/value
This work demonstrates a process using commercial line‐scan SL and embedding a PTFE‐coated micro‐wire that is subsequently removed for producing repeatable and reproducible horizontal embedded micro‐channels of circular cross‐sectional geometries.
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Youjae Yi, Seo Young Kim and Jae Won Hwang
This study aims to examine how social exclusion and the social status of a rejecter affect consumers’ purchase intentions toward ordinary products.
Abstract
Purpose
This study aims to examine how social exclusion and the social status of a rejecter affect consumers’ purchase intentions toward ordinary products.
Design/methodology/approach
Three experiments were conducted to test the hypotheses.
Findings
The status of a rejecter, whether high or low, had a significant influence on individuals’ evaluations of ordinary products. Results showed that individuals who were rejected by a low status source had higher purchase intentions toward the ordinary (vs unique) products compared to those who were rejected by a high status source due to threatened self-concept.
Practical implications
With the increased number of lonely consumers in the market today, firms should pay closer attention to the behavioral patterns of consumers who are socially excluded. In addition, firms should be aware that consumers’ purchase intentions vary depending on the sources of social exclusion.
Originality/value
This paper addresses the significant impact of sources of social exclusion on consumers’ evaluation of ordinary products. Moreover, this study focuses on a relatively neglected definition of social status, namely, the sociometric status, to fill the gap in the social status literature.
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Chunbo Lin, Wenbin Xu, Yuxiong Guo, Chengyong Shi, Jianbo Huang, Taisheng Wang, Hongxin Zhang, Zhankun Weng and Jia Xu
In this paper, a dynamic projection scanning lithography (DPSL) technology and system is proposed to achieve cross-scale 3D printing, addressing the limitations of the traditional…
Abstract
Purpose
In this paper, a dynamic projection scanning lithography (DPSL) technology and system is proposed to achieve cross-scale 3D printing, addressing the limitations of the traditional 3D printing methods that struggle to achieve both large build volumes and high precision. The method achieves a printing accuracy of 10 µm within a build volume of 100 × 100 × 100 mm, and successfully fabricates complex hollow structures and functional models.
Design/methodology/approach
DPSL uses a digital micromirror device (DMD)-based digital projector to generate light patterns for light-curing printing. The light patterns are created by sequentially loading the print design frame by frame, forming dynamic light patterns that are scanned line by line across the material surface for solidifying the printing materials. By controlling the scanning range of the digital projector, it is theoretically able to print models of any size. Additionally, by using DMD oblique scanning, the impact of the DMD micromirrors’ shape and arrangement on print accuracy is addressed by overlapping exposures along the scanning direction of the digital projector.
Findings
This study shows the printing system resolution of 1.3 µm, while the maximum size of the printing model depends on the system scanning range. Additionally, by using DMD oblique scanning, the impact of the DMD micromirrors’ shape and arrangement on print accuracy is addressed by overlapping exposures along the scanning direction of the digital projector.
Originality/value
This work demonstrates that DPSL based on oblique scanning technology is used to achieve 3D printing with high precision, large area and smoother surface. In addition, a rigid release method is used to achieve a precise printing layer thickness in the top-down printing process. By adhering the release film to the bottom surface of the glass and adjusting the descent distance of the stage for each layer, uniform layer thickness can be achieved for each exposure.
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Andreas Andrikopoulos, Andreas Georgakopoulos, Anna Merika and Andreas Merikas
This paper aims to explore the effect of interlocking directorates on agency conflicts and corporate performance in the shipping industry.
Abstract
Purpose
This paper aims to explore the effect of interlocking directorates on agency conflicts and corporate performance in the shipping industry.
Design/methodology/approach
The authors use social network analysis to discover central nodes in the network of personal and corporate connections in an international sample of 110 listed shipping companies.
Findings
Assessing network structure, the authors find that the network of corporate leaders is denser than the network of shipping companies. The network of shipping companies is populated with many isolated nodes; the network of shipping executives and directors is populated with many cohesive groups in which the longest distance between two corporate leaders is two companies. The authors find that interlocking corporate leadership can help resolve agency conflicts in the shipping industry, bearing a negative effect on the magnitude of agency costs. The extent of leadership overlaps is associated with board size, financial leverage and profitability. The relationship between profits and interlocks is bidirectional, implying that interlocking directorates bear a positive effect on asset returns.
Originality/value
The authors map the relational structures in the social networks of companies and company leaders in the shipping industry and discover the cross-sectional determinants of interlocks in the shipping industry. The finding about the effect of interlocks on profitability and agency costs bears policy implications for the design of corporate governance in the shipping industry.