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This paper aims to investigate the common-mode voltage (CMV) issue of a three-phase four-leg voltage-source inverter. A new space vector modulation method, named as three-dimensional active zero state Pulse-width modulation (PWM) (3-D AZSPWM), is proposed to reduce the CMV level.

PWM is a general method to generate the switching signals of the power converters in order to obtain high-quality output voltages. However, the CMV produced by PWM methods has become a serious problem. 3-D AZSPWM is proposed to solve this issue. In 3-D AZSPWM, instead of using zero voltage vectors with high CMV level, appropriate complementary non-zero vectors are introduced to synthesize reference vector. The proposed method is classified into four types of AZSPWM1(a), AZSPWM1(b), AZSPWM2(a) and AZSPWM2(b) based on different complementary vectors chosen for each type. An extend software simulation using MATLAB/Simulink is performed to verify the superior performance of the proposed methods.

Compared to other reduced CMV methods, the proposed method not only reduces the CMV but also retains the positive characteristics of the three-dimensional classical space vector PWM (3-D CSVPWM).

The proposed method does not suffer from linear modulation region limitation and also does not impose additional switching loss. Furthermore, calculated output voltage harmonic distortion factor illuminates acceptable quality of output voltage produced by the proposed method.

This paper aims to propose a suitable atomizing solidification chitosan (CS) gel liquid extrusion molding technology for the three dimensional (3D) printing method, and experiments verify the feasibility of this method.

This paper mainly uses experimental means, combined with theoretical research. The preparation method, solidification forming method and 3D printing method of CS gel solution were studied. The CS gel printing mechanism and printing error sources are analyzed on the basis of the CS gel ink printing results, printing performance with different ratios of components by constructing a gel print prototype, experiments evaluating the CS gel printing technology and the effects of the process parameters on the scaffold formation.

CS printing ink was prepared; the optimal formula was found; the 3 D printing experiment of CS was completed; the optimal printing parameters were obtained; and the reliability of the forming prototype, printing ink and gel printing process was verified, which allowed for the possibility to apply the 3 D printing technology to the manufacturing of a CS gel structure.

This study can provide theoretical and technical support for the potential application of CS 3 D printed gels in tissue engineering.

Presents a standard data format for describing and interpolating 3‐D human body shapes from data collected by a 3‐D body scanner. The body data were treated as a series of horizontal cross‐sections. Each cross‐section was described by 16 data points. The 3‐D surface can be calculated by interpolating between these sections. This procedure allowed editing and manipulation of raw scanned data, as well as substantial data reduction. Horizontal cross‐sections of the body were chosen to correspond to particular anatomical surface landmarks, rather than distances from a reference point. Hence, each data element described a particular anatomical location, irrespective of body shape and size. This feature allowed comparison and averaging of 3‐D shapes, greatly enhancing the application of 3‐D scanned data. The standard data format allows 3‐D scanned data to be transferred into CAD/CAM systems for automated garment design and manikin manufacture.

The material-jetting-type (MJ) 3-D printing technology has advantages in resolution and color printing. During the printing process, a leveling technique is needed to precisely control the thickness and flatness of each layer. Roller-type leveling mechanism has been adopted in commercial MJ 3-D printers, but it is lack of research on roller leveling process parameters and establishing experimental procedures. Therefore, in this study, a roller-type leveling mechanism for a MJ color 3 D printer was developed, and experimental approaches were utilized to determine process parameters.

The roller-type leveling mechanism was chosen to provide functions of flattening and removal of excess material. The parameters studied were roller speed and rotational direction. Surface roughness, Ra, of printed single-layered specimens was measured at 15 locations for plane roughness and along five lines for line roughness to evaluate the leveling results. Adopting suitable parameters, color samples with and without leveling were printed for comparison and verification.

According to plane roughness results, forward rotation achieved better leveling. Plane roughness was the major criteria to determine roller speed with the assistance of standard deviation of line roughness. The best parameters of the self-developed MJ color 3-D printer were found to be rolling forward at 1,100 rpm. In addition, printed color samples showed great improvement in surface roughness with leveling and no obvious color mixing after leveling.

Leveling is important to achieve desired layer thickness, smooth surface and good color quality in color 3-D printing. For MJ 3-D printing, only patents were revealed regarding roller design, but paper publications have not been presented. This research practically proposed to use experimental approach to understand the effects of roller operating parameters and to find the suitable ones based on surface roughness results.

This research established the experimental procedures and also suggested guidelines of experimentally obtaining suitable roller leveling process parameters. Developers can refer to this study results to design and adjust leveling mechanism in a new MJ 3-D printer.

The experimental approach can be applied to similar MJ 3-D printing systems if different materials are introduced or the platform speed is changed. The observed trends suggested several guidelines to plan limited experiments only to obtain suitable roller process parameters.

The aim of this paper is to investigate transverse impact behaviour and energy absorption of 3‐D glass/polyester resin cellular woven composite impacted by flat‐ended rod and to discuss the failure modes of the composite under quasi‐static and dynamic loading.

The quasi‐static compression tests were conducted with MTS 810.23 tester. The impact behaviours of the 3‐D cellular woven composite were tested with a modified split Hopkinson pressure bar (SHPB) apparatus.

Failure loads and energy absorption capacities of the 3‐D cellular woven composite increase as the increase of load speed, i.e. the composite is strain rate sensitive. The failure loads and energy absorptions in warp direction are lower than those in weft direction at the same loading speed because of the lower linear density of warp yarns. The damage morphologies of the 3‐D cellular woven composite manifest the compression failure in the front side and tension failure in rear side.

The influence of different structure parameters on the failure mode should be studied.

The study provided information on the failure mode and energy absorption of the 3‐D cellular woven composite under impulsive loading. This could be used for light weight structure design, such as vehicle and aircraft stringer structures.

Understanding energy absorption of the 3‐D cellular woven composite under transverse impact is much more important than those under quasi‐static loading. This paper provides the results of dynamic mechanical properties of a new kind of 3‐D cellular woven composite under impact loading.

The ability for learners to interact online via their avatars in a 3-D simulation space means that virtual worlds afford a host of educational opportunities not offered by other learning technology platforms, but their use also raises several pertinent issues that warrant consideration. This chapter reviews the educational use of virtual worlds from a design perspective. Virtual-world definitions are explored, along with their key educational characteristics. Different virtual-world environments are briefly contrasted, including Second Life, Active Worlds, Open Sim, and Minecraft. A wide variety of virtual-world uses in schools and universities are examined so as to understand their versatility. Key educational benefits of virtual worlds are distilled from the literature, such as the ability to facilitate 3-D simulations, role-plays, construction tasks, and immersive learning. Emergent issues surrounding the use of virtual worlds are also analyzed, including cognitive load, safety, and representational fidelity. One higher education and one school level vignette are provided in order to offer more detailed insight into the use of virtual worlds in practice. Recommendations for learning design and implementation are presented, based on the thematic analysis of contemporary virtual-worlds research.

This study aims to apply an open-source approach to protect the 3D printing industry from innovation stagnation due to broad patenting of obvious materials.

To do this, first an open-source implementation of the first five conditions of an open-source algorithm developed to identify all obvious 3-D printing materials was implemented in Python, and the compound combinations of two and three constituents were tested on ten natural and synthetic compounds. The time complexity for combinations composed of two constituents and three constituents is determined to be O(n²) and O(n³), respectively.

Generating all combinations of materials available on the Chemical Abstracts Services (CAS) registry on the fastest processor on the market will require at least 73.9 h for the latter, but as the number of constituents increases the time needed becomes prohibitive (e.g. 3 constituents is 1.65 million years). To demonstrate how machine learning (ML) could help prioritize both theoretical as well as experimental efforts a three-part biomaterial consisting of water, agar and glycerin was used as a case study. A decision tree model is trained with the experimental data and is used to fill in missing physical properties, including Young's modulus and yield strength, with 84.9 and 85.1% accuracy, respectively.

The results are promising for an open-source system that can theoretically generate all possible combinations of materials for 3-D printing that can then be used to identify suitable printing material for specific business cases based on desired material properties.

The purpose of this study was for a panel of experts to initially make visual assessments of female body morphotypes from their 3-D scanned images, and, thereafter, use these and their anthropometric data to derive algorithms to specify anthropometric parameters corresponding to a specific body morphotype categories.

This paper presents a method to quantitatively define women's body morphotypes derived from the visual assessments of the 3-D scans of the body. Nine morphotype categories are defined and algorithms are derived to define the range of values of bust-to-waist and hip-to-waist girth ratios corresponding to the different categories. The method showed an 81.9% prediction accuracy between the visually assessed and predicted morphotypes. This compared to a 71.9% prediction accuracy of another published method. This new normative method (NNM) enables a quantitative evaluation of how visual assessments of body morphotypes from different populations of women, made by different assessors, differ.

The panel assessed morphotype category with the largest number of subjects was rectangle (52.0%), followed by spoon (39.5%), hourglass (5.6%) and triangle (2.9%). The NNM shows similar predicted categories, with only slightly differing values, viz. the morphotype category with the largest number of subjects was rectangle (54.1%) followed by spoon (40.4%), hourglass (4.8%), inverted U (0.6%) and Y (0.3%). The morphotype with the worst correlation between the predicted and the assessed was the triangle (0% – 0/10), followed by the hourglass (31.6% – 6/19). The NNM did not generate more than one prediction for a given visually assessed morphotype.

The geographical location of the authors meant that it was convenient to develop and evaluate the NNM from a sample of South African women. Further work can be conducted where a large number of national and international experts perform an assessment of a set of body morphotypes. The anthropometric data derived according to ISO 8559-1 protocols may then be used to determine the criteria used by each assessor with the aim of reaching a consensus and, hence, movement toward body morphotype standardization for both men and women and thereby mass customization.

The advantage of the method is that it provides for a, transparent, universally applicable procedure that is simple to use and implement in the clothing and retail sectors The NNM did not predict more than one morphotype for a given category; hence, it enables objective comparisons to be made between the visual assessments of morphotype categories of different populations by different assessors, to also evaluate how and where the assessments differ.

Studies such as this highlight the need for standardization of both the criteria used in the expert panel visual assessments and an agreement on the anthropometric measures or landmarks required to define women 3-D body morphotypes standardized to international protocols for target market segmenting in the clothing and retail sectors and in industries where variability in body morphotype, size and proportions has ergonomic implications.

The theoretical concept is novel, easy to follow and implement in the clothing and related sectors and has not been published to date. The approach was to develop a theoretical concept standardized to ISO 8559-1 that enable objective comparisons between visual assessments of morphotypes of different populations by different assessors, and to also evaluate how and where the assessments differ. The knowledge and experience of domain experts were to initially conduct the visual assessments of women morphotypes from their 3-D scans and thereafter to use these and their anthropometric data to derive algorithms to specify anthropometric parameters corresponding to a specific body morphotype category.

Three dimensional (3 D) laser scanner surveying is widely used in many fields, such as agriculture, mining and heritage documentation and can be of great benefit for as-built documentation in construction and facility management domains. However, there is lack of applied research and use cases integrating 3 D laser scanner surveying with building information modeling (BIM) for existing facilities in Malaysia. This study aims to develop a scan to as-built BIM workflow to use 3 D laser scanner surveying and create as-built building information models of an existing complex facility in Malaysia.

A case study approach was followed to develop a scan to as-built BIM workflow through four main steps: 3 D laser scanning, data preprocessing, data registration and building information modeling.

This case study proposes a comprehensive scan to as-built BIM workflow which illustrates all the required steps to create a precise 3 D as-built building information model from scans. This workflow was successfully implemented to the Eco-Home facility at the Universiti Teknologi Malaysia.

Scan to as-built BIM is a digital alternative to manual and tedious process of documentation of as-built condition of a facility and provides a detail process using laser scans to create as-built building information models of facilities.

To realize stable and precise localization in the dynamic environments, the authors propose a fast and robust visual odometry (VO) approach with a low-cost Inertial Measurement Unit (IMU) in this study.

The proposed VO incorporates the direct method with the indirect method to track the features and to optimize the camera pose. It initializes the positions of tracked pixels with the IMU information. Besides, the tracked pixels are refined by minimizing the photometric errors. Due to the small convergence radius of the indirect method, the dynamic pixels are rejected. Subsequently, the camera pose is optimized by minimizing the reprojection errors. The frames with little dynamic information are selected to create keyframes. Finally, the local bundle adjustment is performed to refine the poses of the keyframes and the positions of 3-D points.

The proposed VO approach is evaluated experimentally in dynamic environments with various motion types, suggesting that the proposed approach achieves more accurate and stable location than the conventional approach. Moreover, the proposed VO approach works well in the environments with the motion blur.

The proposed approach fuses the indirect method and the direct method with the IMU information, which improves the localization in dynamic environments significantly.