Due to polymeric wear debris causing osteolysis from polymer, metal ions causing metallosis from metal, and brittle characteristic causing fracture failure from ceramic in the application on bearing of total hip prosthesis requires the availability of new material options as a solution to these problems. Polycrystalline diamond (PCD) has the potential to become the selected material for hard-on-hard bearing in view of its advantages in terms of mechanical properties and biocompatibility. The present study contributes to confirming the potential of PCD to replace metals and ceramics for hard-on-hard bearing through von Mises stress investigations. A computational simulation using a 2D axisymmetric finite element model of hard-on-hard bearing under gait loading has been performed. The percentage of maximum von Mises stress to respective yield strength from PCD-on-PCD is the lowest at 2.47%, with CoCrMo (cobalt chromium molybdenum)-on-CoCrMo at 10.79%, and Al2O3 (aluminium oxide)-on-Al2O3 at 13.49%. This confirms that the use of PCD as a hard-on-hard bearing material is the safest option compared to the investigated metal and ceramic hard-on-hard bearings from the mechanical perspective.

Autonomous vehicle is a vehicle that can automatically navigate both long-range and short-range navigation. In this paper, we designed a motion and navigation control system of an autonomous vehicle that is implemented on a mobile robot. The remote navigation process involves using the global positioning system (GPS) sensor as a reference to navigate, and for short-range navigation using the proximity and force sensor. The robot task is to reach several coordinate points that are determined and marked with a traffic-cone at each point. In the control of short-range navigation, the robot uses five ultrasonic and three switch sensors to read the environment as input to the description of the distance between the robot and the object. The micro-controller then compares it to the robot’s safe distance instructions in navigating with surrounding objects. GPS sensor is used to provide remote navigation path information. To compensate for the accuracy of the wide GPS sensor readings, several waypoints are designed to guide the robot to the specified traffic-cone. From the implementation, the robot movement can go along the navigation area and can avoid short-range objects in the robot trajectory and get to the traffic-cone point with the percentage of success reaching the final destination above 86% both in sunny and cloudy weather.

Environmental factors, especially climate, soil and pest attack, are limiting factors in citrus production. The purpose of this study was to determine the limiting factors on RGL citrus productivity. This research was carried out in 2019 in Pal VII Village, Bermani Ulu Raya District, Rejang Lebong Regency, Bengkulu Province with seven farmers at the research location. Data was collected from primary and secondary data consist of 10 years climate data, soil characteristics and citrus pest and diseases identification, which are then analyzed descriptively. The results showed that the productivity of RGL citrus in the research location was influenced by high rainfall during the fruiting period. Another limiting factor is the relatively low soil nutrient content because farmers generally do not apply fertilization technology that based on crop needs. Pests and diseases that had been potential reduced the productivity and quality of citrus fruits were fruit borers, fruit flies and scurvy, and climate factors also influenced the quality.

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Applying a speed control system to a mobile robot needs to be done to make the robot move stably in an uneven environment with the variation of load. This study purpose is to designed a speed control system for a mobile robot to follow setpoints with a fast response to reach a predetermined speed. The speed controller used the fuzzy logic control method. The input is a speed error and the change in speed error is known from an encoder sensor and the output of the system is pulse width modulation (PWM) in the range of 8-bit converted to fuzzy forms. The rule formation and rule analysis with its implication function use the MIN function and defuzzification use the weighted average method. By implementing this fuzzy control the results of the robot move at the speed corresponding to the setpoint both on flat or uneven terrain, with load or without load. In experiments carried out on robots with a setpoint of 9,000 rpm from rest, the response time (in rise-time) is less than 47ms and steady-state error close to zero.