Journal of Research and Applications in Mechanical Engineering

Research on Communication Analysis between Vehicles and Pedestrians at Unsignalized Crosswalks Using Online Video

G. Bamba, D. Misaki — Tue, 28 Nov 2023 00:00:00 +0700

In recent years, considerable attention has been paid to research on communication in self-driving vehicles. However, few studies have quantitatively evaluated and clarified the relationship between modern vehicles and pedestrians. Additionally, communication methods and gestures are perceived differently in different countries and regions. In the past, quantitative research on communication that differed across countries and regions often required research teams to travel across countries to conduct research, which entailed enormous costs and a heavy burden. In this study, we propose an online video-based pedestrian behavior analysis and compare pedestrian communication in Japan and U.S. based on a questionnaire survey. Results with the proposed algorithm reveal that Japanese pedestrians tend to use eye contact as a form of communication at unsignalized crosswalks, whereas American pedestrians tend to use hand-raising movements. Moreover, the gesture choices of pedestrians in both countries vary based on the strength of their authority on the road.

Analysis and Design for Vibration of a Wing-Like Laminated Composite Panel with Blended Layers

Y. Narita — Tue, 28 Nov 2023 00:00:00 +0700

An analytical method is presented to study the bending vibration of a cantilevered, laminated composite rectangular panel having blended layers. The panel (plate) having blended layers is modelled as a laminated plate in which the outer layers have subdivisions with non-identical fiber orientation. A finite element program is also coded to clarify accuracy of the present method. In numerical examples, the natural frequencies computed by the proposed method show very good agreement with those from the FEM code. Use of this fast and accurate method is suggested in vibration design, for example, optimization of fundamental frequencies.

Design and Analysis of Double Element Airfoil Using RANS

J. Chaiyanupong, C. Khajorntraidet — Tue, 28 Nov 2023 00:00:00 +0700

This paper aims to design the double-element airfoil for application on the front wing of a student formula car by using CFD (computational fluid dynamics) with the Reynolds Averaged Navia-Stokes (RANS) model. The design method is done by simulating the flow on a single-element airfoil to determine the separation point of fluid on the airfoil surface. The point is then used to divide the airfoil into the double-element airfoil, followed by analysis to find the right angle to achieve maximum downforce. The simulation results indicated that the angle of attack of 3° and the second element wing angle of 30° give the maximum Cl of 4.837, which can create downforce on the front wing of 884.3 N. It can be concluded that the designed double-element airfoil provides better downforce values than a single-element airfoil.

Numerical Study of LPG Combustion Affected by Y-Shaped Nozzle Mounted on Slot Burner

Tue, 28 Nov 2023 00:00:00 +0700

This research is to study the LPG combustion affected by Y-shaped nozzle mounted on slot burner. The Y-shaped nozzle is a burner outlet which controls the air and fuel flow on the slot burner. In order to increase temperature by improvement of the mixing between air and fuel over the burner, the Y-shaped nozzle mounted on the slot burner was designed and investigated by numerical method. This study focused on main parameters as 15, 30, and 45 degrees of air circulating cavity angle with/without air strengthening hole by numerical simulation model at equivalence ratio Φ =1.0 and 2.0 kW of firing rate. As the result, more 423.15 K (11.0%) of maximum flame temperature was increased with Y-shaped nozzle slot burner mounted with 45 degrees of air circulating cavity angle and added air strengthening hole. This study shows the enhancement of LPG flame temperature influenced by the Y-shaped nozzle mounted on the slot burner due to the improvement of mixing flow.

Analysis of Motor Unit Recruitment in Human Skeletal Muscle Using Finite Element Method

P. Wongnarkpet, A. Wisessint — Tue, 28 Nov 2023 00:00:00 +0700

Motor unit recruitment is an essential factor in understanding muscle behavior. Skeleton muscle is associated with force generation and transmission to perform daily activity. The present study aims to compare the number of motor units recruited in human skeleton muscle by finite element analysis. The finite element model is constructed based on the mechanism of the sarcomere. The geometry of the model is focused on the fascicle level which consists of many fibers and is enveloped with an endomysium sheet. Each subunit of fiber is compressible and elongated similar to the sliding filament theory. The fully instrumented model provides information on self-contraction and force distribution along the skeletal muscle. The result of contraction behavior from the finite element model can be applied to designing functional ankle-foot orthosis for various physiology of humans. Results show that the equal distribution of muscle fiber type in a single fascicle achieves the greatest outcome in isotonic contraction toward other activation patterns. The culmination of contraction behavior from the finite element model can be applied to designing functional ankle-foot orthosis for various physiology of humans.

Parametric Study on Water-Cooling Plates to Improve Cooling Performance on 18650 Li-ion Battery

R. Nanthatanti, J. Charoensuk, M. Masomtob, S. Hirai — Tue, 28 Nov 2023 00:00:00 +0700

With a novel NSTDA design, pressure drop, and standard deviation of cooling water velocity inside the channel of the liquid cooling plate were evaluated under various channel counts [2, 3, 4, and 6 channels per base], inlet temperatures of water [25, 30, 35, and 40 °C], and inlet velocity of water [0.5, 1.0, 2.0, and 3.0 m/s] at steady-state conditions. It was found that the 4-channel design produced the most distributed flow with an inlet water velocity of 0.5 m/s. The average channel velocity was 0.0371 m/s. When increasing the inlet velocity of water, a larger pressure drop was observed. Simulation of heat transfer on a single row, single cooling channel design of a battery pack was performed with a channel velocity of 0.03 m/s, which imitates the 4-channel design under the heat generation produced at a charging rate of 0.75 C. An inlet temperature of 30 °C was used to keep the maximum temperature of the battery at 30.706 °C. The temperature difference over the battery pack was approximately 0.4 °C.

Evaluation Method for Robot Interfaces Considering Psychological Safety

Y. Horikoshi, D. Misaki — Wed, 10 Jan 2024 00:00:00 +0700

Service robots have been implemented across various sectors in recent years to enhance work efficiency. Developing interfaces with an emphasis on usability from a human-centered design perspective is crucial. Numerous evaluation methods have been suggested for robot interfaces, including those focusing on work efficiency and error rate reduction. Although the NASA-TLX safety evaluation method can assess specific indicators in hazardous situations, an evaluation methodology that emphasizes psychological safety is required. In this study, we propose an evaluation approach that considers psychological safety, utilizing a differential two-wheeled robot. Furthermore, we conducted experiments using three different interfaces. The result of empirical experiments elucidated that interfaces characterized by elevated psychological safety engendered a proclivity among participants towards diverse exploratory methodologies and the adoption of venturesome undertakings. Conversely, interfaces marked by diminished psychological safety precipitated impediments for participants, largely attributed to the palpable absence of tactile reinforcement, thereby obfuscating the stimulation of audacious endeavors. Such revelations accentuate the paramountcy of cognizing the nuanced gradations in psychological safety that modulate the propensity for immersion in exigent tasks. Psychological safety pertains to an individual's perception of the consequences of engaging in interpersonal risk-taking. Thus, it is necessary to explore psychological safety assessment models for various interfaces and conduct surveys among study participants to develop a highly accurate model. In the future, we should also consider control models for automobiles and other vehicles.

Experimental Investigation of Optimal Pressure Achieved through Rubber Foam Extension in the Curing Process

T. Naemsai, W. Suksuwan, T. Wissamitanan, T. Petdee — Wed, 17 Jan 2024 00:00:00 +0700

The aim is to determine the optimal expansion pressure of the rubber foam in the mold to determine the curing time that ensures good mechanical properties. In the experiment, the temperature was examined in three levels: 130, 140, and 150°C, for 20 min. Additionally, 8 compounds were examined with either DPT or ADC blowing agents. The experiment results indicated that the compressive stress and absorbed energy showed a similar trend, which was directly changed by both temperature and blowing agent. The appropriate compounds were compound 4 with 12 phr ADC and compound 5 with 3 phr DPT with the optimal pressure of 0.22 bar and 0.17 bar, respectively. Both ensured the high absorbed energy and high compression set. By determining the optimal internal pressure, the energy consumption of the NR foaming process can be calculated. In addition, the energy consumption was significantly changed by the area ratio.

Effect of Injection Frequency on Actual Fuel Injection Rate of Piezoelectric Diesel Fuel Injector

J. Boonjun, N. Kammuang-lue — Fri, 19 Jan 2024 00:00:00 +0700

The objectives of this research was to investigate the effect of injection frequencies (IF) on the actual fuel injection rate (Act.FI) and discrepancy between Act.FI and ideal fuel injection rate (Ideal.FI) of a piezoelectric diesel fuel injector (PDF). IF and duty-times (Dt) of injector control signal (ICS) were varied from 8.33 Hz to 33.33 Hz and 200 μs to 2,000 μs respectively. Moreover, difference pressure (Dp) and fuel temperature (Ft) were varied from 800 bar to 1,600 bar and 25 ^oC to 45 ^oC respectively. It was found that when the IF increased, the Act.FI proportionally increased with a higher gradient compared with an increase of the Ideal fuel injection rate (Ideal.FI) at a certain Dt. The minimum Act.FI was shown at lowest IF equaled to 12.9 g/min appearing at Dp and Ft of 800 bar and 45°C. The maximum Act.FI was shown at highest IF equaled to 190 g/min appearing at Dp and Ft of 1,600 bar and 25°C. The discrepancy was directly proportional to the IF which demonstrated the maximum value of 7.7 g/min or equaled to 4.07% compared to Ideal.FI at IF of 33.32 Hz appearing at Dt, Dp and Ft of 2,000 μs, 1,600 bar and 45°C. These were affected by nozzle closure delay which was consequently influenced by the movement of an injector needle. The benefits obtained from this research could be utilized by compensating the Act.FI to be close to the Ideal.FI in the actual operation of a common rail direct injection diesel engines.

Efficiency Evaluation on Cooling Behavior of Water-Cooling Jacket for Synchronous Reluctance Motor

Mon, 29 Jan 2024 00:00:00 +0700

This study presents the cooling efficiency after installing a water-cooling jacket for a 3-kW synchronous reluctance motor of an electric motorcycle and the factors influencing its thermal behavior by experimental and simulation approaches. The testing process was conducted as a method to collect input parameters and validate the results of the computing simulation. The simulation procedure used the step running technique to evaluate two different water-path models. The findings indicated that the maximum temperature of the stator winding and jacket cover decreased by 19.12 °C and 16.07 °C, respectively, following the installation of the water jacket and operation at a low flow rate with a current supply of 200 A. Furthermore, increasing the water flow rate leads to a substantial decrease in maximum temperature before a certain flow rate; 2 liters per minute (LPM) was chosen as the optimal rate. Temperature fluctuations exhibit an upward trend up to 1.85 °C with the higher supplied currents but drop with a higher flow rate. In addition, the motor maximum temperature in the long water-path jacket (LWJ) model was lower than in the short water-path jacket (SWJ) model due to the higher heat transfer coefficient (HTC).

The Optimization of Electrostatic Air Filter Layers for Small Dust Particles Reduced

C. Chutakositkanon, E. Sangthammarat, P. Keangin — Sat, 03 Feb 2024 00:00:00 +0700

Air pollution, stemming from natural and industrial sources, necessitates effective air purification methods. Electrostatic air filters offer an eco-friendly alternative to high-efficiency particulate air (HEPA) filters, characterized by low pressure drop, minimal noise, cost-efficiency, and reusability. This study investigates the enhancement of electrostatic air filter performance by increasing layer count. Experimental tests in a 1×1×1 m³ chamber, using small dust particles (1 µm, 2.5 µm, and 10 µm), reveal that adding layers significantly improves filtration efficiency. Optimal layer counts of 5, 5, and 4 for respective particle sizes maintain compliance with ASHRAE 52.2 MERV Rating 14 standards. According to ISO16890 standards, these filters require maintenance or replacement after 72 cycles when efficiency falls below 60%. This research promotes wider adoption of electrostatic filters for health benefits and energy conservation.

Evaluation for Optimal Configuration of Twisted Fiber Bundle Wick Heat Pipe with Top Heat Mode

J. Simsiriwong, R. Wanison, P. Sakulchangsatjatai, P. Terdtoon, N. Kammuang-lue — Sat, 03 Feb 2024 00:00:00 +0700

The objective of this research was investigating the thermal resistance of the twisted fiber bundle wick (TFBW) heat pipe. TFBW was made by combining between both size copper fiber of 30 μm and 50 μm. These were arranged as the lengthwise and twist together. The variable parameters of the TFBW were focused on the mixing ratio and twisting pitch length. TFBW heat pipe with outer diameter of 3 mm and length of 70 mm was heated in the top heat mode. Heat input was maintained as constant value at the evaporator section. The condenser section was cooled by air. The outer surface of both sections was measured temperature which were using for calculating the thermal resistance. It was observed that the mixing ratio of 50%:50% demonstrated the lowest thermal resistance for twist pitches of 10 mm and 15 mm. Due to the appropriate pore size of the formed wick, it provided high capillary pressure and high permeability. The decreasing of twist pitch (tighter twisting) caused to increasing of thermal resistance. This was because an excessive twist resulted in very small pore sizes led to lower permeability. The mixing ratio of 50%:50% with a pitch length of 20 mm exhibited an opposite trend because that already had the appropriate pore size. Moreover, the twisting with a smaller pitch had smaller pores leading to a higher capillary pressure. Therefore, the optimal configuration of TFBW providing the lowest thermal resistance was the mixing ratio of 50%:50% with a pitch length of 10 mm.

Redesign of the Mini Hydro Turbine Structure Using Finite Element Analysis (FEA) to Solve Resonance Problem

P. Sreejai, A. Promwungkwa, K. Ngamsanroaj — Wed, 07 Feb 2024 00:00:00 +0700

This study investigates the structural redesign of a mini hydro turbine system in an effort to solve the turbine shaft resonance problem. The original design of the turbine shaft support is examined to identify the root causes of the problem, which result in the failure of the turbine bearings. In order to approximate the natural frequencies, finite element analysis (FEA) models are developed and verified through comparison with experimental data, which may consist of modal analysis, coast-down testing, and deflection tests. Experimental results deviate from the FEA analysis of mode 1 frequency by 6.81%. Analysis of the linear dynamic response reveals that the amplitude of the shaft coupling's vibrations during system start-up and shutdown exceeds the allowable design parameters; this is the primary cause of bearing damage. FEA is used to redesign the shaft structural support in order to eliminate the natural frequencies. Modes 1 and 2 exhibit frequency shifts of 14.57 to 38.16 Hz and 11.36 to 37.57 Hz, respectively. These values are double the frequency at which a typical generator operates. The maximum shaft support deflection is reduced from 0.25–0.39 mm to 0.01 mm, according to the FEA results. Utilizing the redesign parameters, a new shaft support will be constructed. To confirm the FEA results, it is possible to monitor and recheck the data.

Semantic Mapping and Voice User Interface Based on ORB-SLAM and YOLO for Navigating Visually Impaired Person

Q. Wang, Y. Shikanai, K. Mima, K. Tobita — Tue, 13 Feb 2024 00:00:00 +0700

As the world's population grows and life expectancy increases, the number of visually impaired people is increasing. We developed a visual navigation map for visually impaired people to solve their life problems. This map combines the navigation map generated by Visual SLAM with the semantic information of the landmark detected by the YOLO object-detection algorithm to create a map that can be used for voice navigation and other purposes. To help visually impaired people find what they want in their daily lives, we have also developed a voice user interface based on YOLO object detection, which is a relatively lightweight voice recognition system that can help visually impaired people solve problems in their lives.

Behavior of Plane Synthetic Jets Passing Over Two-Dimensional Flat Plates

K. Suzuki, K. Nishibe, K. Sato — Thu, 15 Feb 2024 00:00:00 +0700

Airflow control in railway and aircraft cabins, including air-conditioning and ventilation, is attracting increasing attention. Jet technology is typically employed for performing such controls. Synthetic jets, known for their inherent unsteadiness, have been investigated as an alternative to continuous jets, yielding diverse results. Researchers have endeavoured to elucidate the flow characteristics of synthetic jets in asymmetric flow fields. However, the relationship between the partition plate, which corresponds to a seat in a guest room, and jet flow remains unclear. Notably, studies investigating the flow characteristics when a partition plate is installed downstream of a synthetic jet are rare. In this study, the effects of a two-dimensional row of flat plates on the flow characteristics of a planar synthetic jet is investigated by installing multiple partition walls downstream of the slot. Flow visualization, velocimetry, and numerical simulations are performed, and the relationship between the recirculating flow and dimensionless frequency is discussed.