Journal of Quality Engineering and Management

Abstract The reliability of manufactured products can vary according to changes in production quality. Field failure data provide useful information for assessing whether changes in reliability are significant or identifying the cause of changes. In order to identify these errors, we need to model the effect of these errors on product reliability. In this research, we intend to predict product reliability behavior based on the percentage of different quality errors with which products may be produced. In this regard, two types of quality errors, namely non-compliant items and assembly error are examined separately. In order to model, it is assumed that the percentage of qualitative errors follow the beta distribution and the failure times follow the Weibull distribution. Reliability, risk rate and probability chart of products are studied under these two types of qualitative errors. Based on the results of this research, it is possible to guess the type and percentage of quality errors with which products are produced.

Abstract Positioning the car in the parking lot is an important factor to make the parking lots smarter, as a result of which it is possible to steer the car, which will be a factor to increase the quality of service in the parking lot. Due to the closed environment of the parking lot, locating objects in it, including locating objects in indoor environments. The use of radio waves and related methods to locate indoors is one of the solutions presented in this field. In some other methods in this field, the location of the object in the indoor space is calculated only by using the equipment available in the environment (similar to location radars). Disadvantages of both methods include the need for additional equipment at high prices, extreme sensitivity to environmental conditions and existing noise. In this research, an attempt has been made to perform the location process by using monopole antennas and scattering matrix. For this purpose, first, the parking environment is simulated with a plate containing several monopole antennas, and using finite element-based software, the scatter matrix is ​​obtained for the absence and presence of the object in different environmental conditions that have been simulated. After calculating the scattering matrices, the required data are selected and each of these values ​​is assigned to an object position using a neural network. In the next phase, in exchange for placing the object in the new position, the corresponding scattering matrix is ​​obtained and the object is calculated by comparing it with the information collected in the previous step. This process is similar to the fingerprint algorithm, except that instead of using the values ​​of signal strength, the matrix is ​​scattered. The advantages of this method include no need to calibrate and accurately measure the position of the antennas, scalability and provide a new solution to reduce costs and increase the accuracy of calculating the position of the object.

Abstract Control charts are one of the most important tools for evaluating process performance and monitoring. In the classic design of a control chart, the cost of quality depends on whether the quality characteristic is inside or outside the control. The use of loss function in the design of control charts, as an estimator of the cost of production of defective products, contributes to a more comprehensive assessment and better management decisions. Therefore, in this article, the combination of loss function and economic statistical design of control charts. The loss functions used so far in this field have been symmetric functions, but in many cases overestimating or underestimating the ideal value for a quality characteristic does not produce the same losses. Therefore, for the first time in the literature on the design of control charts, this paper uses the asymmetric loss function of Linux. Using a practical example, the performance of quadratic, linear, exponential and linear loss functions are compared. The result of these comparisons showed that the Linex loss function has the lowest cost in statistical-economic design of the control chart compared to other loss functions.

Abstract The purpose of this study is to provide a suitable model for advanced product quality planning at the level of defense organizations, so that all design-related requirements are considered seamlessly and consistently throughout the idea-to-product process. In this research, different models of advanced product quality planning were studied and based on the AIAG standard model [1], different models were compared and compared. Then, based on the knowledge of internal and external stakeholders of the design process, a list of their requirements was determined and based on that, the steps and documents of each model phase were selected and determined. Finally, the proposed model for six products was reviewed in the design offices and the conformity assessment was performed. According to the results of this research, the main problem of product quality planning in the design stage is the lack of full knowledge of stakeholders and their requirements.

Abstract The aim of this study was to provide a model to explain the relationship between quality requirements and service quality dimensions in Iranian universities. The research method was descriptive survey and the statistical population included academic experts, managers and staff as well as customers of Islamic Azad universities in Fars province. Using purposive sampling method, 30 experts were selected and by stratified random sampling, 415 managers and employees and 464 customers were selected. Data collection tools were questionnaires of quality requirements and dimensions of service quality, which were developed by the researcher after studying the theoretical foundations and research background, and its validity and reliability were estimated and approved. To analyze the data, one-sample t-test and structural equation model were used with the help of AMOS software. The results showed that the status of quality requirements (M = 3.57) and the status of service quality dimensions (M = 3.19) are in a relatively desirable range, in other words, considering the significance level of α ≤ 0.05 and appropriate. Existence of fitness indicators This model can be used to determine the relationship between the components of quality requirements and dimensions of service quality in Islamic Azad universities of Fars province. Also, the research results showed that only professional obligation predicts the dimensions of service quality and moral, competitive and accountable obligation do not predict the dimensions of service quality.

Abstract The purpose of this study is to help buyers of liquefied natural gas to select different contracts and the level of purchase in different time periods. Some of these contracts have a general discount and some have a promotion. Important factors in contracts are evaporation rate, quality and operating costs. Using Linamp technique, the weight and the best level of each of the above factors are determined. Then, with a mathematical model of mixed integer, the contract selection, the optimal purchase amount of each contract and the type of discount used in each period are determined by considering the purchase amount from the current market by the buyer. The numerical model is based on real data and the mathematical model is solved based on Gomez software. The results show that out of 12 contracts offered to the buyer, only 5 contracts have been selected, of which 2 contracts have used the development discount and 3 contracts have used the general discount.