• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.24 no.64
• /
• pp.29-38
• /
• 2001

Most warranty studies assume that the usage intensity is the same for all buyers. However, in real life the usage intensity varies across the population of buyers. In the general case, one can divide the population into $\kappa$ categories. This has implications for manufacturers of products. Should a manufacturer produce one product and offer different warranties for the $\kappa$ groups or produce different products (one for each group) and offer the same warranty. A warranty cost analysis is needed to choose between these options. The analysis complicated by factors such as adverse selection , buyers attitude to risk and the price structure. In this paper we develop models to study the expected warranty cost for products with free replacement warranty with varying usage intensity. Numerical examples are presented.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.28 no.3
• /
• pp.142-148
• /
• 2005

대부분의 일차원 보증정책에 대한 비용분석은 소비자 사용률이 모든 사용자들에게 동이란 것으로 가정하고 있다. 하지만 현실적으로 사용률은 소비자에 따라서 다르기 때문에, 일반적인 경우 소비자 집단을 ${\kappa}$ 범주로 나눌 수 있다. 즉, 동일한 제품에 대해서 생산자는 ${\kappa}$ 범주에 속하는 다른 보증정책을 제시할 수 있고, 보증비용은 이런 옵션들 가운데 소비자가 자기의 입장에 맞는 보증기간을 선택할 수 있다. 본 논문에서는 소비자의 사용률이 변화하는 경우를 고려한 무료보증정책을 갖는 기대보증비용 모형을 분석하고, 이에 따른 수치예제를 제시한다.

• Journal of Information Processing Systems
• /
• v.12 no.3
• /
• pp.436-454
• /
• 2016

This research presents the battery discharge rate models for the energy consumption of mobile phone batteries based on machine learning by taking into account three usage patterns of the phone: the standby state, video playing, and web browsing. We present the experimental design methodology for collecting data, preprocessing, model construction, and parameter selections. The data is collected based on the HTC One X hardware platform. We considered various setting factors, such as Bluetooth, brightness, 3G, GPS, Wi-Fi, and Sync. The battery levels for each possible state vector were measured, and then we constructed the battery prediction model using different regression functions based on the collected data. The accuracy of the constructed models using the multi-layer perceptron (MLP) and the support vector machine (SVM) were compared using varying kernel functions. Various parameters for MLP and SVM were considered. The measurement of prediction efficiency was done by the mean absolute error (MAE) and the root mean squared error (RMSE). The experiments showed that the MLP with linear regression performs well overall, while the SVM with the polynomial kernel function based on the linear regression gives a low MAE and RMSE. As a result, we were able to demonstrate how to apply the derived model to predict the remaining battery charge.

• Journal of Korea Society of Industrial Information Systems
• /
• v.7 no.1
• /
• pp.66-74
• /
• 2002

Warranty cost analysis for one-dimensional warranties assumes that the usage intensity (or rate) is the same for all buyers. In real life the usage intensity varies across the population of buyers. Also for products sold with warranty, preventive maintenance actions by manufacturers and buyers have a significant impact on the total costs for both parties. In this paper we deals with models to study the expected warranty cost for products with free repairable warranty with varying usage intensity and three types of preventive maintenance. We also review the literature which links warranty and maintenance and develops a framework to define new topics for research in the future and examines a new model formulation. It then develops a new model and carries out its analysis.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.7 no.1
• /
• pp.33-38
• /
• 2012

As underwater channel is very complex and time-varying, don't supports good-quality for communication service. In this paper, a multi-carrier CDMA(MC-CDMA) system for the reliability and robust service in the underwater acoustic channel is proposed and analyzed for its performance. Applied variable rate algorithm to the proposed system gets a channel state information from relationship between SINR and user data-rate. Using channel state information make spectrum usage more efficient and overall system performance improved. In this paper, the performance of proposed system analyzed by simulation. And Pseudo-Random spread codes used in the system are discussed.

• Journal of Information Science Theory and Practice
• /
• v.11 no.4
• /
• pp.40-50
• /
• 2023

Research in interdisciplinary fields like biomechanics is published in a variety of journals whose visibility depends on bibliometric indexing that is often driven by citation analysis of bibliometric databases. This study documented variation in publication metrics and research subject categories assigned to 14 biomechanics journals. Authors, citation, and citation rate (CR) were collected for the top 15 cited articles in the journals retrieved from the Google Scholar service. Research subject categories were also extracted for journals from three databases (Dimensions, Journal Citation Reports, and Scopus). Despite the focus on biomechanics for the journals studied, these biomechanics journals have widely varying CR and subject categories assigned to them. There were significant (p=0.001) and meaningful (77-108%) differences in median CR between average, low, and high CR groups of these biomechanics journals. Since CR are primary data used to calculate most journal metrics and there is no one biomechanics subject category, field normalization for journal citation metrics in biomechanics is difficult. Care must be taken to accurately interpret most citation metrics of biomechanics journals as biased proxies of general usage of research, given a specific database, time frame, and area of biomechanics research.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.7
• /
• pp.799-808
• /
• 2016

The IEEE 802.15.7r1 Task Group (TG7r1), known as the revision of the IEEE 802.15.7 Visible Light Communication standard targeting the commercial usage of visible light communication systems which mainly use either image sensors or cameras, is of interest in this paper. The vast challenge in Image Sensor Communications (ISC), as it has been addressed in the Technical Consideration Document (TCD) of the TG7r1, is the Image Sensor Compatibility to support the variety of different commercial cameras available on the market. The on-going ISC standard must adhere to compatible image sensors regulations. This paper brings an inside review of the TG7r1 and an inside look of related works on Image Sensor Communications. The paper analyzes the compatibility features by introducing a revised model of receiver to explain how those features are necessary. One of the most challenging but interesting features is the capability in being compatible to camera frame rates. The variation of camera frame rate is modeled from verified experimental results. Noticeably, three singular approaches to support frame rates compatibility, including temporal approach, spatial approach, and frequency-domain approach, are proposed on the paper along with concise definitions. Those schemes have been presented as valuable proposals on the call-for-proposal meeting series of the TG7r1 recently.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.20 no.4
• /
• pp.245-251
• /
• 2008

The cooling load in winter is significant in buildings and hotels because of the usage of office equipments and the high efficiency of wall insulation. Hence, the development of a multi-heat pump that can cover heating and cooling simultaneously for each indoor unit is required. In this study, the operating characteristics and performance of a simultaneous heating and cooling heat pump in the heating-main operating mode were investigated experimentally. The system adopted a variable speed compressor with four indoor units and one outdoor unit with R-410A. In the heating-main mode, the cooling capacity was lower than the design cooling capacity due to the reduction of the flow rate in the indoor unit for the cooling, with the increase of the heating capacity. To solve these problems, the performance characteristics of the simultaneous heating and cooling heat pump in the heating-main mode were investigated by varying the flow rate to the indoor unit for the cooling and the compressor rotating speed. In addition, the adequate control methods were suggested to improve the system efficiency.

• The Journal of the Korea Contents Association
• /
• v.12 no.4
• /
• pp.10-19
• /
• 2012

Seamless streaming of multimedia content that ensures Quality of Service over heterogeneous networks has been a desire for many multimedia services, for which the multimedia contents should be adapted to usage environments such as network characteristics, terminal capabilities, and user preferences. Scalability in video coding is a good feature to meet the requirement of heterogeneous networks. In this paper, we propose a dynamic adaptation scheme of H.264/AVC SVC bit-stream using the MPEG-21 Digital Item Adaptation (DIA) tool. MPEG-21 DIA framework provides systematic solutions in choosing an adaptation operation to given conditions and supports interoperable video adaptation. The experiment results show that the proposed adaptation scheme provides QoS-enabled delivery and consumption of SVC with time-varying constraints of network, terminal, and user preference, in a robust and efficient way. In particular, the proposed adaptation scheme is proved to work well with very low delay under the condition that the variation rate of the given network bandwidth is upto 62%.

• International Journal of Internet, Broadcasting and Communication
• /
• v.10 no.3
• /
• pp.26-34
• /
• 2018

In this paper, we propose a scheduling scheme that can efficiently serve I/O requests having deadlines in flash storage. The I/O requests with deadlines, namely, real-time requests, are assumed to be issued for streaming services of continuous media. Since a Web-based streaming server commonly supports downloads of HTMLs or images, we also aim to quickly process non-real-time I/O requests, together with real-time ones. For this purpose, we adopt the well-known rate-reservation EDF (RR-EDF) algorithm for determining scheduling priorities among mixed I/O requests. In fact, for the use of an EDF-style algorithm, overhead of task's switching should be low and predictable, as with its application of CPU scheduling. In other words, the EDF algorithm is inherently unsuitable for scheduling I/O requests in HDD storage because of highly varying latency times of HDD. Unlike HDD, time for reading a block in flash storage is almost uniform with respect to its physical location. This is because flash storage has no mechanical component, differently from HDD. By capitalizing on this uniform block read time, we compute bandwidth utilization rates of real-time requests from streams. Then, the RR-EDF algorithm is applied for determining how much storage bandwidth can be assigned to non-real-time requests, while meeting deadlines of real-time requests. From this, we can improve the service times of non-real-time requests, which are issued for downloads of static files. Because the proposed scheme can expand flexibly the scheduling periods of streams, it can provide a full usage of slack times, thereby improving the overall throughput of flash storage significantly.