Cucuk Nur Rosyidi

Cooperative inventory model for vendor-buyer system with unequal-sized shipment, defective items and carbon emission cost

We develop an integrated inventory model for single-vendor single-buyer with deterministic demand. The vendor’s production process may be deteriorated during production run and results to some defective items. The defective probability is assumed to be uniformly distributed. The shipment from vendor to buyer is made in unequal size over multiple shipments. We also incorporate the carbon emission cost and investigate the environmental impact on the model. The results of the study show that adopting unequal-sized shipment policy in the model which considering defective items will result in lower carbon emission cost and total cost compared to an equal-sized policy. Furthermore, the increase in defective probability will lead to the increase of carbon emission cost.

PRIORITIZING KEY CHARACTERISTICS

Key characteristics (KCs) priority has to be determined by manufacturing company to help them in determine which KC has the most influence to the manufacturing cost and quality loss. This paper proposes a simple method to prioritize key characteristics using pareto diagram based on the result of an optimization model. The model is developed to find optimal tolerance and process characteristics of KCs. The objective function of the optimization model is to minimize the manufacturing cost and quality loss. Vice jaw is used as an example to illustrate the implementation of the model.

A collaborative supply chain inventory model with defective items, adjusted production rate and variable lead time

This paper proposes a production-inventory model for supply chain system consisting of single-vendor and single-buyer. The buyer uses periodic review policy to manage his inventory. The lead time is formulated by considering production time and transportation time. Moreover, the demand in buyer side is assumed to be normally distributed and the shortage is assumed to be fully backordered. The production process maybe deteriorated during production time hence the lot received by the buyer may contain some defective items. The defective rate of the items is assumed to be fixed. The objective of the proposed model is to determine review period, production rate and number of deliveries to minimise the joint total cost. An iterative procedure is proposed for finding the solutions of the model. A numerical example and sensitivity analysis are illustrated to show the models behaviour.

Optimization Models for Deriving Optimum Target of Key Characteristics

The aim of this research is to develop optimization models in deriving optimum target of key characteristic (KC). There are two kinds of product KCs introduced in this paper, namely performance and dimension product KC. The performance product KC target values must be determined by balancing customer and designer utilities subject to design cost and time provided by a company. The KCs of a product can be visualized using a KC flow-down which shows the hierarchical structure of the product. The flow-down may consist of many levels from product KC to process KC. Using axiomatic design as a methodology to map the flow-down, we conclude that product KC, assembly-components KC, and process KC are in functional domain, physical domain, and process domain respectively. In this paper, the objective function of the model for deriving optimum product KC target is to minimize utility gap between customer and designer subject to design cost and time. The assembly-component KCs have to be derived considering the product KC targets. In the absence of product KC target, the objective function of the model is to maximize the desired effect or minimizing the undesired effect. In the existence of product KC target, the objective function of the model is to attain the target considering technical constraints of the product. We use a shaft design problem as a numerical example to show the implementation of the models.

Mismatch analysis of elementary school desk and chair key characteristics in Indonesia

In this research we analyze the mismatch between desk and chair key characteristics and the respective pupil’s anthropometric data. Sample is taken from11 public elementary schools in six regions in Central Java Indonesia. Mismatch comparisons are made among existing desk and chair, Indonesia National Standard (SNI) dimensions of desk and chair, and dimensions from pupil’s anthropometric data. From the results of the analysis, seat height and desk height have the highest mismatch, while seat width and under desk clearance have the lowest mismatch. In general, four key characteristics dimensions from pupil’s anthropometric data are considered to have better match compared to existing and SNI key characteristics dimensions. A redesign is needed due to the results of the analysis.

Multi-objective optimization model of CNC machining to minimize processing time and environmental impact

Minimizing processing time in a production system can increase the efficiency of a manufacturing company. Processing time are influenced by application of modern technology and machining parameter. Application of modern technology can be apply by use of CNC machining, one of the machining process can be done with a CNC machining is turning. However, the machining parameters not only affect the processing time but also affect the environmental impact. Hence, optimization model is needed to optimize the machining parameters to minimize the processing time and environmental impact. This research developed a multi-objective optimization to minimize the processing time and environmental impact in CNC turning process which will result in optimal decision variables of cutting speed and feed rate. Environmental impact is converted from environmental burden through the use of eco-indicator 99. The model were solved by using OptQuest optimization software from Oracle Crystal Ball.

A concurrent optimization model for suppliers selection, tolerance and component allocation with fuzzy quality loss

Abstract The aim of this paper is to develop an optimization model to optimally select suppliers and allocate components to the selected suppliers. The objectibve function of the model is to minimize purchasing cost and fuzzy quality loss. Using fuzzy quality loss, the assembly quality may be divided into several grades allowing the fuzziness in the resulted assembly tolerance. The model considers several constraints such as production capacity, assembly quality, and process and technological capability of the suppliers. A numerical example is given in this paper to show the implementation of the model. Sensitivity analysis is performed to determine the effect of process capability to the supplier selection, components allocation and total cost. The increase of process capability in one of the suppliers affects the selection and component allocation mainly when the process capability increase from 1 to 1.5. Further, increasing the process capability index to 2 has no effect on the selection and allocation but affects the fuzzy quality loss and hence reduces the total cost.

Effect of furniture weight on carrying, lifting, and turning of chairs and desks among elementary school children

Rearranging furniture in elementary school classrooms encourages classroom activities. In elementary schools in Indonesia and some other developing countries, usually only one style of furniture is used for all children, and the furniture is heavy and oversized for younger children. This affects their ability to carry it. The objective of this study is to investigate the effects of elementary school furniture weight and children’s age on performance of three carrying tasks (carrying a chair, lifting and turning a chair on a desk, and carrying both a chair and a desk together), from the ergonomics point of view. A total of 42 schoolchildren (ages 6–9; 17 Indonesian, 25 Japanese) participated in this study. Two types of Japanese chairs (Chair A and B, weight: 3.2 kg and 3.9 kg), one type of Indonesian chair (Chair C, weight: 5.0 kg), and two types of desks (height: 58 cm and 68 cm) were used. Indonesian chairs took significantly longer time to carry than the two Japanese chairs, and there was a significant negative relationship between age and task time for Chairs B and C, but not Chair A. Success rates for lifting and turning the chair declined as age decreased and chair weight increased, but were not significantly influenced by desk height. Success rates for carrying a chair and desk together significantly decreased with heavier furniture. Children aged six showed an extremely low success rate in almost all conditions. In conclusion, children’s ability to carry furniture is affected by their age and furniture characteristics, especially weight. In order to encourage classroom activities in elementary school, school furniture should be of appropriate weight. Supervision for younger children is required during classroom furniture arrangement.

Monte Carlo Simulation of Gas Spring in an Energy Storing Prosthetic Knee

Gas Spring is an important component of an energy storing prosthetic knee. The spring stored energy during flexion and released the energy while in the extension. In this research, we discuss a Monte Carlo simulation model of a gas spring in an Energy Storing Prosthetic Knee (ESPK) using Oracle Crystal Ball software. The simulation is used to predict the effects of three important design variables of a gas spring which are cylinder diameter, cylinder length, and displacement to the energy storing performance of the spring. The results of simulation show that there are two design variables which have significant contribution to the variations of energy storing performance: cylinder diameter and displacement. Those design variables account for 99.3% to the total variance of energy storing. Quality improvement must be conducted to lowering the resulted energy storing variance. We proportionally decrease the variance of the design variables to lowering the energy storing variance. The simulation results show a significant quality improvement of about 50% in term of energy storing standard deviation. The results also show that cylinder diameter is more sensitive than the other two design variables in energy storing quality improvement.

Simultaneous component and tolerance allocation through suppliers’ selection considering technological capability and production capacity to minimise purchasing cost and quality loss

In this paper we investigate component and tolerance allocation through supplier selection model. The model contributes to the current literature by incorporating simultaneous allocation of component and tolerance policy which has not been considered in almost all of previous models. The objective of the model is to minimise purchasing cost and quality loss considering supplier’s technological capability and production capacity. Numerical example is provided to show the implementation of the model and sensitivity analysis is performed to explore the effect of key parameters on selected suppliers, amount of allocation and total cost. The results of sensitivity analysis indicate that the changes on technological capability and production capacity will affect the optimisation result in which the model will tend to select the suppliers which have the lower price comparing to the selected suppliers in numerical example.