A Method for Generation of a Sizing System and Representative Models for a Facial Mask Design

A sizing system and representative face models (RFMs) need to be properly determined for the design of a facial mask. The present study proposed a novel approach for the generation of a sizing system and RFMs for a facial mask that considers not only the accommodation of the target population but also its applicability in practice (e.g., ease of use and economic efficiency). A custom sizing system with four unique sizing categories was generated by applying the proposed approach for a pilot oxygen mask for Korean pilots. Then, out of 336 faces, a face showing the minimum value of weighted sum of Euclidean distance (WSED) was identified as the RFM of each of the four sizing categories. The proposed approach can be applied to the development of a sizing system and the identification of representative human models for the design of wearable products associated with multiple body dimensions

인간공학적 제품 설계를 위한 형상 기반 백분위 대표인체모델 생성 방법

Objective: A novel method based on body shape for the generation of representative human models (RHMs) was proposed in the present study for ergonomic product design. Background: RHMs of a particular population are required to satisfy the representativeness of a target population under consideration in ergonomic product design. A conventional RHM generation method based on key anthropometric dimensions has limitations in terms of the representativeness of RHMs and consistency between RHMs. Method: This study proposed a method of shape-based percentile RHM generation using template-registered 3D body images. A point cluster containing all 3D body images of a particular vertex is projected on a vector passing the origin point and the average location of the point cluster; then, a percentile location of the point cluster is calculated. Then, a percentile RHM is generated by forming a triangular mesh structure based on the percentile locations of all the vertices. Lastly, the generated RHM is adjusted in terms of its size by referring to anthropometric measurements. Results: The RHMs generated by the proposed method showed better representativeness for ergonomic product design as well as better morphological consistency between RHMs as compared to the conventional method. Conclusion: Compared to the conventional method that chooses a few cases from a large number of 3D body scan images in a database, the proposed method uses all the 3D scan images in a database to generate RHMs. Application: The proposed method can be applied for the ergonomic design of wearable products such as facial masks, glass-type or goggle-type products, industrial protective devices, sporting goods for athletes, medical prosthetics, and assistive tools.22Nkc

The clinical effect of sodium hypochlorite oral rinse on peri-implantitis lesion: A pilot study

Peri-implantitis poses an imminent challenge to the field of implant dentistry. Considering the promising findings of sodium hypochlorite and periodontal lesions, the aim of the present study was to evaluate the clinical effects of sodium hypochlorite oral rinse on peri-implantitis lesions. Twelve peri-implantitis patients were instructed to rinse with 15 mL of a fresh solution of 0.25% sodium hypochlorite for 30 s twice a week for 3 months. At baseline and 3-month visits, probing depth and modified sulcular bleeding index were recorded at 6 points per lesion (mesiobuccal, buccal, distobuccal, mesiolingual, lingual, and distolingual). Individual and total bacterial loads of 18 pre-designated species of microorganisms were analyzed by real-time PCR methods. Probing depth decreased after the experiment, with an average difference of 1.1 mm and a standard deviation of 1.7 mm. The modified sulcular bleeding index decreased by a mean value of 0.8 with a standard deviation of 1.1. This study demonstrated the clinical effects of sodium hypochlorite oral rinse on peri-implantitis lesions and the reduction of periodontal probing depth and gingival bleeding index. This study suggested that the concentration of 0.25% be used for treatment of peri-implantitis

Vibroacoustic analysis of dental air turbine noise

Objective The objective of this study is to analyze the noise mechanism of dental air turbine handpiece with vibroacoustic simulation. Materials and methods The operational part of the Gentle Silence Lux 8000B (KaVo Dental GmbH) was disassembled and scanned. The scanned data were rendered to smooth irregularities and then virtually reassembled. The rendering was 3D mesh modeled for the analysis. And, the interior void space and exterior space was mesh modeled as air layer. As per simulation input informations, the material property of steel was provided for the handpiece components. Supplied air pressure of 0.22 MPa at the inlet and static temperature of 25 degrees C was provided as operating conditions. Twenty virtual microphones were arrayed to measure the noise. Vibroacoustic noise simulation was performed with ACTRAN 2021 (MSC software corporation). Results The mean value of noise ranged from 49.88 to 66.38 dB while the peak value ranged from 69.53 to 81.64 dB depending on the microphone position. All microphones showed the similar noise pattern which had peak amplitude at around 4500 Hz. The calculated natural frequency of interior air layer was 4478.92 Hz and 7573.77 Hz. Discussion The simulated result showed similar tonal noise of dental handpiece suggesting air resonance phenomenon as a possible cause of dental handpiece noise. Conclusion Vibroacoustic analysis of the air layer contained within the dental air turbine handpiece showed the resonance peak noise at 4478.92 Hz under the simulated conditions.N

손 치수 측정을 위한 3차원 반자동 측정 방법 개발

22kc

Usability Comparison between 2D and 3D Control Methods for the Operation of Hovering Objects

This paper experimentally analyzed the cognitive load of users based on different methods of operating hovering objects, such as drones. The traditional gamepad-type control method (2D) was compared with a control method that mapped the movement directions of the drone to the natural manipulation gestures of the user using a Leap Motion device (3D). Twenty participants operated the drone on an obstacle course using the two control methods. The drone’s trajectory was measured using motion-capture equipment with a reflective marker. The distance traveled by the drone, operation time, and trajectory smoothness were calculated and compared between the two control methods. The results showed that when the drone’s movements were mapped to the user’s natural directional gestures, the drone’s 3D movements were perceived as more natural and smoother. A more intuitive drone control method can reduce cognitive load and minimize operational errors, making it more user friendly and efficient. However, due to the users’ lack of familiarity with Leap Motion, it resulted in longer distance and time and lower subjective satisfaction; therefore, a more improved 3D control method over Leap Motion is needed to address the limitations

A Method for Generation of a Sizing System and Representative Models for a Facial Mask Design

A sizing system and representative face models (RFMs) need to be properly determined for the design of a facial mask. The present study proposed a novel approach for the generation of a sizing system and RFMs for a facial mask that considers not only the accommodation of the target population but also its applicability in practice (e.g., ease of use and economic efficiency). A custom sizing system with four unique sizing categories was generated by applying the proposed approach for a pilot oxygen mask for Korean pilots. Then, out of 336 faces, a face showing the minimum value of weighted sum of Euclidean distance (WSED) was identified as the RFM of each of the four sizing categories. The proposed approach can be applied to the development of a sizing system and the identification of representative human models for the design of wearable products associated with multiple body dimensions.11Ysciescopu

A framework for effective face-mask contact modeling based on finite element analysis for custom design of a facial mask.

A novel contact model is presented to efficiently solve a face-mask contact problem by using the finite element (FE) method for the optimized design of a custom facial mask. Simulation of contact pressure for various mask designs considering material properties of the face allows virtual evaluation of the suitability of a mask design for a person's face without conducting empirical measurement of the face-mask contact pressure. The proposed contact model is accomplished by combining three approaches to reduce the calculation cost of simulating the face-mask contact: (1) use of a simplified and modifiable mask model that applies a spline curve to design points; (2) reduction of the FE model of the face by applying static condensation; and (3) application of a contact assumption that uses the Lagrange multiplier method. A numerical case study of a medical mask design showed that the proposed model could calculate the face-mask contact pressure efficiently (0.0448 sec per design). In a pilot usability experiment, the measured contact pressure was found similar values (range of mean contact pressure: 0.0093 ~ 0.0150 MPa) to the estimated values (range of mean contact pressure: 0.0097 ~ 0.0116 MPa)

Traditional and 3D scan extracted measurements of the heads and faces of Dutch children

3D anthropometry has created a significant opportunity for designers to improve fit by offering detailed information regarding the shape of the human body. Various researchers have shown the benefit of using 3D anthropometric data in the development or evaluation of head related products for adults. However, detailed 3D anthropometric data of children heads and faces is still lacking. This paper presents up to date descriptive statistics of detailed measurements made of heads and faces of Dutch children. For the purpose of developing ergonomic head and face wear for children, an anthropometric survey was conducted, whereby children aged 6 months to 7 years were measured, utilising both traditional anthropometric measurement techniques and 3D image derived measurements. The traditional measurements were compared with the most recent dataset of Dutch children and, on a more detailed level, with a dataset of North American children

Development of a Virtual Fit Analysis Method for an Ergonomic Design of Pilot Oxygen Mask

In the ergonomic design of wearable products such as an oxygen mask, systematic design methods including the analysis of anthropometric information, evaluation of fit, and product design need to utilize 3D human scan data. The present study intends to develop a virtual fit analysis method that generates an ergonomic shape of an oxygen mask for fighter pilots based on 3D facial scans. The proposed virtual fit analysis method enables iteratively to revise the shape of an oxygen mask until an appropriate level of fit between the mask and a group of pilot faces is achieved. The proposed method of virtual fit analysis and design optimization was applied to find ergonomic shapes of oxygen masks for four size categories (small narrow, medium narrow, medium wide, and large wide) to accommodate 336 pilots of the Republic of Korea Air Force. The virtual fit analysis results in the study showed that the revised oxygen mask shapes achieved significantly higher accommodation percentages (4.8 similar to 88.7%) at facial areas (nasal root, nasal side, cheek, and chin) compared to the existing oxygen mask shapes. The proposed method can be applied to develop an ergonomic product design that fits the face and other human body parts.11Ysciescopu