• Journal of the Institute of Electronics Engineers of Korea CI
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• v.38 no.4
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• pp.22-32
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• 2001

In this paper, we propose an average acquisition time and hardware design of high speed PN code synchronous acquisition system using DMF(Digital Matched Filter) with new switching method in DS-SS/CDMA(Direct Sequence Spread Spectrum Code Division Multiple Access). In reality, the PN code synchronous acquisition system using DMF has very complicated hardware, high cost and high power consumption. The PN code synchronous acquisition system using proposed switching method DMF can overcome those disadvantages. Therefore, we can make hardware simple and obtain low power and high density by reducing the area by 1/5 against the conventional approaches of using either the matched filters or the serial correlators. The proposed system architecture is also simple and easily controllable since there is no square-term circuit after execution of digital filtering.

• The Journal of the Acoustical Society of Korea
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• v.16 no.5
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• pp.5-11
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• 1997

In this paper, we investigate the performance of the direct sequence/spread spectrum multiple access (DS/SSMA) system using the Trellis coded modulation (TCM) technique in both multipath fading and multi-user channel environments. For this, an expression that represents the pairwise bit error probability of the system is derived. Unlike the existing results that were performed in a more restrictive condition considering only the multi-user effect, the effects of the multipath fading as well as the multi-user environments are compositely taken into account. In order to check the validity of our analysis, although not direct, computer simulations are carried out, and they show that our expression matches exactly with the previous work for which the TCM and the multipath effects were disregarded. Moreover, it is observed that the performance of the Trellis coded DS/SSMA system can be improved dramatically comparing to the uncoded QPSK system in the multipath fading and multi-user channel environments.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.4
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• pp.87-97
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• 2020

The livestock infections had been happened seasonally, but they have gradually changed to be irrelevant to seasons and have an aspect to rapidly spread after outbreak. Especially in Korea, proactive disinfection measures are very important because the livestock farms are located densely so high as to accelerate the spread of disease between farms. livestock disease outbreaks like HPAI and FMD occurred with high probability due to vehicles visiting the farms, this study is to evaluate the efficiency of livestock vehicle disinfection systems by investigating the disinfectant coverage according to the type of vehicle disinfection system and the type of vehicle quantitatively. In field experiments, water-sensitive papers (WSPs) were attached to 21 locations on the surface of four vehicles (sedan, SUV, truck, and feed transport), respectively, and exposed to disinfectants while the vehicle was sprayed in two vehicle disinfection systems (tunnel type and simplified type). The WSPs were scanned and image-processed to calculate the disinfectant coverage. The results showed that the tunnel-type vehicle disinfection system had a better disinfection performance with an average coverage of 90.27% for all vehicles compared to 32.62% of the simplified type system. The problem of the simplified system was a wide coefficient of variation (1.05-1.31) of the disinfectant coverage between 21 locations indicating a need for further improvement of nozzle location and arrangement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.10 s.89
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• pp.1011-1017
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• 2004

Ultra Wideband(UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geolocation, and other applications. The energy of UWB signal is extremely spread from near DC to a few GHz. This means that the interference between conventional narrowband systems and UWB systems is inevitable. However, the interference effects had not previously been studied from UWB wireless systems to conventional mobile wireless systems sharing the frequency bands such as Korean Cellular CDMA and WCDMA. This paper experimentally evaluates the interference from two kinds of UWB sources, namely a direct-sequence spread-spectrum CDMA(DS-CDMA) UWB source and an impulse radio UWB source, to a Cellular CDMA and WCDMA digital transmission system. The average frame error rate degradation of each system are presented. From these experimental results, the interference effects of DS-CDMA UWB source is not severe compared to the Impulse UWB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.2
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• pp.179-187
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• 2010

The use of high frequency band, broad band and MIMO antenna is expected in the next generation mobile communication system. By the rapid increase of demand for wireless communications and the explosive increase of the mobile communication services, researches for optimization of next-generation mobile communication system are required. In the existing MIMO channel models, propagation-environments are commonly classified into urban, suburban, rural area, etc. However such approaches can have drawbacks in that many different morphologies may exist even in the urban area, for example. In this paper, we introduced path morphology concept, and proposed the method of morphology classification considering the building height, density, etc. Delay spread(DS), angular spread(AS) of AoD and AoA analyzed for each environment using the ray tracing technique. Based on the analysis, a MIMO channel model appropriate in domestic environment was suggested.

• Fire Science and Engineering
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• v.30 no.3
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• pp.31-40
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• 2016

Recently, a curtain wall system was applied to skyscrapers to prevent fire spreading along the vertical direction due to stack effect and outside air flow when a fire breaks out in skyscraper. Conventional sprinklers cannot prevent the spread of fire to the upstairs areas, which increases the loss of life and property. In this study, a water curtain nozzle that creates wider water coverage on the surface of glass and can prevent the spread of fire to the upstairs areas was developed. The spray pattern of the water curtain nozzle was compared with that of a sprinkler to determine performance of the water curtain nozzle. A fire experiment was constructed on the second floor to verify performance of the water curtain nozzle in preventing the spread of fire to the upstairs areas. The fire and watering experiment proved that the water curtain nozzle prevented more effectively the spread of fire than the conventional sprinkler. The position of first crack and critical temperature of fracture were also analyzed using numerical analysis.

• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.79-85
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• 2023

Recently, in the semiconductor process, large companies are seeking process changes from memory semiconductors to the foundry due to the increase in demand due to the 4th industry. industry is expanding. The characteristics of special gases and precursors, which are raw materials used to produce these semiconductor chips, are toxic, pyrophoric, inflammable, and corrosive. These semiconductor raw materials are operated in a closed system and do not leak to the outside during normal times, but when leaked, they spread to the inside of the gas box, and when proper ventilation is not provided inside the gas box, they spread to the outside, causing fires, explosions, or toxic substances. It can lead to major accidents such as leakage. Recently, there have been cases of accidents in which hazardous materials leaked from the closed system of the semi conductor process and spread to the inside and outside of the gas box. . In this study, we propose preventive measures based on the case of an accident in which raw material leaked from the VCR fitting, which is the connection part of the semiconductor raw material transfer pipe, and spread to the outside of the gas box.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.223-223
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• 2000

Embedded system area has brought an innovation and has been spread rapidly by the growth of the Internet, wireless telephony and multimedia recently. Many embedded systems are required to be real-time systems in that it needs multi-tasking and priority based scheduling. This paper introduces a real-time system that was developed with web server ability for control and monitoring system employing a real-time operating system. It discusses the design model, structure, and applications of web server system. We used SNDS100 board which has a 32-bit RISC microcontroller of ARM7TDMI core as a hardware platform. MicroC/OS kernel was used as Real-time operating system that supports a preemptive and multitasking functions. We developed a hierarhchical control and monitoring system that not only reduced system and management costs, but also enhanced reusability and portability.

• Journal of the Optical Society of Korea
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• v.19 no.4
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• pp.421-426
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• 2015

This paper presents a hybrid single optical system for an LED surgical light that combines the advantages of both lens- and reflector-type single optical systems. The proposed hybrid single optical system includes a lens in the center and the LED light originating from the lens is redirected using a reflector to achieve a high beam spread. Iterative optical software simulations are used to provide data for the design of the lens and reflector for a single optical system, and for a complex optical system for the LED light assembly. The resulting data is also used to fabricate a prototype system. Experiments using the prototype of the hybrid single optical system and a mock-up LED surgical light confirm the system's shadow dilution performance and its applicability to surgical operations.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.354-357
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• 1991

In the case of system operation, a line overload cause damage to spread an whole range of power system. Of the theorems on load shedding, this study applied power distribution theorem and load reduction theorem which are local load shedding method, which are not affected by the magnitude of the power system and need not a large memory capacity and computation time. In this paper, we treat the problem of overload when power system occurred to fatal fault. Especially, there is the special case that local load shedding theorem is not always solved. Therefore, we introduce a solved device of the problem and construct the expert system of expanded local load shedding. Because proposed method uses the merits of expert system, in the case of system operation, the system operator don't embarrass to fatal fault and promptly deals with.