• The Journal of the Acoustical Society of Korea
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• v.20 no.7
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• pp.101-108
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• 2001

In this paper we focus on dynamic reservation slot allocation scheme for supporting QoS of a voice traffic in WATM MAC. Especially, voice traffic is the most important real-time object, and so we propose a new MAC protocol for voice traffic over WATM networks in the multimedia environment. According to the characteristics of voice traffic which is repeatedly in silent state and active state, new protocol allocates reservation slots dynamically with respect to the number of silent voice source of which starting time is stored to the state table in base station (BS). The simulation results show that the proposed protocol has better performance than slotted ALOHA in average access delay, collision rate, better than NC-PRMA(Non Collision Packet Reservation Multiple Access) in band width efficiency, and can provide a certain level of QoS requirement by the given slot assignment even though the number of voice terminals is increased.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.4
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• pp.317-326
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• 2020

In this study, damages caused by flash fire, overpressure, and thermal radiation based on the sizes of leak holes were evaluated using the areal location of hazardous atmospheres when natural gas leaked owing to the damage of pipeline in a LNG fueled ship. In addition, environmental variables (wind speed, atmospheric temperature, and atmospheric stability) and process variables (pipe pressure and pipe length) were classified to analyze the damage impact ranges caused by various scenarios. From the results, the damage range caused by the environmental variables was the largest, followed by overpressure and thermal radiation. Additionally, for the process variables, regardless of the pressure, length, or size of the leak holes, the damage range attributed to flash fire was the most significant, and the damage range was high in the order of overpressure and thermal radiation, similar to the environmental variables. The larger the size of the leak holes, the higher the values of the environmental and process variables, and the higher the damage range caused by jet fire compared to the environmental variables.

• Fashion & Textile Research Journal
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• v.20 no.4
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• pp.379-388
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• 2018

The Hawaiian shirt, also known as the Aloha shirt, is a short-sleeved, colorful shirt with traditional Polynesian designs (e.g., hibiscus, fish) originating in Hawai'i. The shirt was selected for study because it is a unique garment that originated in the Hawaiian Islands in the late $19^{th}$ and $20^{th}$ centuries and marketed as a tourist product but was eventually adopted as appropriate residential clothing by the $mid-20^{th}$ century, however with different aesthetic details. Today, it is assumed by Hawaiian Island residents that tourists demonstrate poor taste when selecting a Hawaiian shirt. The purposes of this study are to examine the validity of the assumption that tourist taste and resident taste in Hawaiian shirts are different and to investigate the current Hawaiian shirt market change. For this study, 555 questionnaires were obtained from tourists and residents, and 10 Hawaiian shirt retailers/wholesalers participated in in-depth interviews. The results indicated that differences do exist between tourists' and residents' preferences for print designs and colorway. The market change of Hawaiian shirts was also recognizable in that an increasing number of tourists select Hawaiian shirts similar to resident customers, as part of their routine lives rather than as holiday or vacation garments. Other differences in Hawaiian shirt shopping behavior included the findings that tourists consider fabrication less important than resident customers who consider fabrication more (i.e., cotton 100%). By using both quantitative and qualitative methods, this study contributes to the fashion design and marketing field as well as help manufacturers and retailers with their merchandise and distribution plans.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3309-3328
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• 2017

The application of Internet of Things (IoT) in the next generation cellular networks imposes a new characteristic on the data traffic, where a massive number of small packets need to be transmitted. In addition, some emerging IoT-based emergency services require a real-time data delivery within a few milliseconds, referring to as ultra-low latency transmission. However, current techniques cannot provide such a low latency in combination with a mice-flow traffic. In this paper, we propose a dynamic resource reservation schema based on an air-interface slicing scheme in the context of a massive number of sensors with emergency flows. The proposed schema can achieve an air-interface latency of a few milliseconds by means of allowing emergency flows to be transported through a dedicated radio connection with guaranteed network resources. In order to schedule the delay-sensitive flows immediately, dynamic resource updating, silence-probability based collision avoidance, and window-based re-transmission are introduced to combine with the frame-slotted Aloha protocol. To evaluate performance of the proposed schema, a probabilistic model is provided to derive the analytical results, which are compared with the numerical results from Monte-Carlo simulations.

• Journal of Ocean Engineering and Technology
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• v.32 no.4
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• pp.272-278
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• 2018

Recently, the use of hazardous chemicals has been continuously increasing. Therefore, the international trade volume is growing and chemical accidents have increased. Nowadays, the safety awareness of the public has increased. As a result, the management and supervision of hazardous chemicals have been strengthened. However, the port policy of Korea has focused on increasing the volume of cargo through facility development. Thus, the port management of hazardous chemicals has been relatively neglected. For national economic growth and society, the port management of hazardous chemicals should be considered to efficiently ensure safety and economic growth. Therefore, this study assumed scenarios where hazardous materials were moved in a dangerous container, not only on appropriate wharfs but also in ports that were close to a big city. The BTX substances were selected among the toxic chemicals with large import and export volumes, and the risk distance and damage effects were predicted using various risk assessment programs. It is expected that this could be used to improve a port safety management system and could be utilized to determine the safety distance in case of an accident.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.5
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• pp.12-20
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• 2008

RFID(Radio frequency indentification) technology, that the reader detect the tag information attached on the objects without contact, is considered the kernel of realizing tile Ubiquitous Sensor Network. Particularly, because there are lots of tags(which the reader have to detect) in the UHF RFID system(that is applied at the Logistic & Distribution industry). In the UHF RFID system the negative effects, we called the tag-collision, may occur and we should solve these effects. So, in the EPCglobal Gen2 protocol they present the Slotted Random Anti-collision algorithm to prevent the tag-collision effect. In this paper, in order to minimize the tag-collision effect and bring on the system efficiency, we propose the Power Increasing Method that controls the transmission power of the reader depending on the environment and verily the improved performance.

• Journal of the Korean Society of Safety
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• v.32 no.2
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• pp.52-58
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• 2017

One of the most important elements of the management of chemical accident is threat zone estimation of fires, explosions and toxic gas dispersion based on chemical releases. The threat zone estimation is going to be standard of emergency response for the first defender and base line data of off-site risk assesment (hereinafter referred to as "ORA") and risk management plan (hereinafter referred to as "RMP"). Generally, ALOHA form EPA(U.S.) and Kora(from KOREA MINISTRY OF ENVIRONMENT) has been used for the off-site consequence analysis in Korea. However it is hard to predict accurate consequences rapidly in case of emergency. Hydrochloric acid is a multipurpose raw material used in many industrial applications such as chemical, metal and food industries. It is usually treated in concentrations from 10 ~ 35 %, and release accident have occurred frequently. In this study, we have developed a simplified estimating method and equation to calculate threat zone easily in case of emergency due to release accident of hydrochloric acid.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7A
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• pp.756-765
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• 2004

Using single carrier frequency RFID system in one-to-multiple wireless communications, might be generated data loss because of data collisions. Conventional Anti-collision method prevent data loss from data collisions which are binary tree method and ALOHA. However, those two preventive measures also have week points which are strongly dependent on the time and space when passing through the recognition area. This paper suggests the full-length instruction code method which fits in to half-duplex method, prevents data collision effectively by calculating the non-transmitting time of multiple tags considering approaching time to the recognition area. After full-length instruction code method test using 13.56MHz bandwidth RFID system shows that full-length instruction code method could make better result than any other methods. Moreover, the record shows O(n) result after analyzing O-notation of conventional time-domain procedure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12A
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• pp.1311-1319
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• 2007

This paper presents the VHDL implementation procedure of the passive RFID tag operating in Ultra High Frequency. The operation of the tag compatible with the EPCglobal Class1 Generation2(GEN2) protocol is verified by timing simulation after synthesis and implementation. Due to the reading range with relatively large distance, a passive tag needs digital processor which facilitates faster decoding, encoding and state transition for enhancement of an interrogation rate. In order to satisfy linking time, the pipe-line structure is used, which can minimize latency to serial input data stream. We also propose the sampling strategy to decode the Preamble, the Frame-sync and PIE symbols in reader commands. The simulation results with the fastest data rate and multi tags environment scenario show that the VHDL implemented tag performs faster operation than GEN2 proposed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7B
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• pp.518-527
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• 2008

Tag collection is one of the major functions in Radio Frequency Identification (RFID) systems. IS0/IEC 18000-7 defines the tag collection algorithm using the anti-collision algorithm, based on the framed slotted ALOHA for active RFID systems. However, it has inefficiency problems that reduce tag collection performance by deciding non-optimum slot size or using point-to-point commands to put collected tags to sleep. In this paper, we propose two mechanisms to overcome the inefficiency problems and improve tag collection performance: 1) a new slot size decision mechanism to allow the reader to choose the optimum slot size flexibly and 2) a broadcast-based sleep mechanism to put collected tags to sleep effectively. We also implemented an active RFID system, composed of an active RFID reader and multiple tags, and the reader is designed to maximize tag collection performance when the proposed mechanisms are applied. In experiments, we evaluated the tag collection performance using one reader and 50 tags in the real-world environment. The experimental results show that when two mechanisms are applied and the initial number of slots is chosen appropriately, the performance of the proposed tag collection algorithm is greatly enhanced, compared with that of the standard.