• The KSFM Journal of Fluid Machinery
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• v.2 no.3 s.4
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• pp.45-51
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• 1999

Centrifugal fans are widely used and the noise generated by these machines causes one of the most serious problems. In general, the centrifugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the flow discharged from the impeller and the cutoff in the casing. However, only a few researches have been carried out on predicting the noise due to the difficulty in obtaining detailed information about the flow field and casing effects on noise radiation. The objective of this study is to develop a prediction method for the unsteady flow field and the acoustic pressure field of a centrifugal fan and to calculate the effects of rotating velocity, flow rate, cut-off distance and the number of blades and its effects on the noise of the fan. We assume that the impeller rotates with a constant angular velocity and the flow field around the impeller is incompressible and inviscid. So, a discrete vortex method (DVM) is used to model the centrifugal fan and to calculate the flow field. The force of each element on the blade is calculated with the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The cut-off distance is the most important factor effecting the noise generation. Acoustic pressure is proportional to 2.8, which shows the same scaling index as the experimental result. In this paper, the cut-off distance is found to be the dominant parameter offecting the acoustic pressure.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.4
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• pp.561-567
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• 2013

Some of the feature vectors for speech recognition are rare and unusual. These patterns lead to overfitting for the parameters of the speech recognition system and, as a result, cause structural risks in the system that hinder the good performance in recognition. In this paper, as a method of removing these unusual patterns, we try to exclude vectors whose norms are larger than a specified cutoff value and then train the speech recognition system. The objective of this study is to exclude as many unusual feature vectors under the condition of no significant degradation in the speech recognition error rate. For this purpose, we introduce a cutoff parameter and investigate the resultant effect on the speaker-independent speech recognition of isolated words by using FVQ(Fuzzy Vector Quantization)/HMM(Hidden Markov Model). Experimental results showed that roughly 3%~6% of the feature vectors might be considered as unusual, and therefore be excluded without deteriorating the speech recognition accuracy.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.8
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• pp.1181-1187
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• 2016

The objective of the study was to evaluate fattening performance, carcass value and meat quality in pigs of Prestice Black-Pied breed in relation to slaughter weight (SW) and gender (barrows and gilts, resp.). Pigs were divided into weight categories: SW1 (75 to 99.9 kg), SW2 (100 to 109.9 kg) and SW3 (110 to 130 kg) and all individual traits were analyzed by the general linear model procedure (SAS 9.3). Average SW of each weight group was as follows: SW1 94.2 kg, SW2 105.8 kg, and SW3 115.2 kg. Differences among average backfat thickness of 36.07 mm in SW1, 40.16 mm in SW2, and 43.21 mm in SW3 were significant (p<0.01). Lean meat content was 48.94% (SW1), 48.78% (SW2), and 48.76% (SW3). Pigs were slaughtered at average weight of 105.7 kg for barrows and 104.4 kg for gilts. Average backfat thickness for barrows was 40.90 mm and 38.72 mm for gilts (significant difference p<0.05). Lean meat content was 48.75% in barrows and 48.91% in gilts. The values of pH45, characterizing the meat of very good quality. The loin in SW3 was darker than the muscles of SW1 and SW2. Drip loss was the lowest in SW1 (1.96%), compared to the highest drip loss in SW3 (2.59%). Content of intramuscular fat was 2.68% in SW3, 2.79% in SW2, and SW1 had the lowest content 2.47%. The values of pH45, colour lightness and drip loss were similar in both genders. However barrows had higher intramuscular fat content by 0.31% than gilts (p<0.05).

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.2
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• pp.187-191
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• 2017

Objective: An experiment was conducted to examine the effect of dietary supplementation of dried and ground foliage of black gram (Vigna mungo L.) on feed intake and utilization, and production performance of crossbred lactating cows. Methods: Eighteen lactating crossbred (Bos taurus${\times}$Bos indicus) cows (body weight $330.93{\pm}10.82kg$) at their second and mid lactation (milk yield $6.77{\pm}0.54kg/d$) were randomly divided into three groups of six each in a completely randomized block design. Three supplements were formulated by quantitatively replacing 0, 50, and 100 per cent of dietary wheat bran of concentrate mixture with dried and ground foliage of black gram. The designated supplement was fed to each group with basal diet of rice straw (ad libitum) to meet the requirements for maintenance and milk production. Daily feed intake and milk yield was recorded. A digestion trial was conducted to determine the total tract digestibility of various nutrients. Results: The daily feed intake was increased (p<0.05) with the supplementation of black gram foliage. Although the digestibility of dry matter, organic matter, crude protein, and ether extract did not vary (p>0.05), the fibre digestibility was increased (p<0.05), which ultimately improved (p<0.05) the total digestible nutrients content of composite diet. Although, the average milk yield (kg/animal/d) and composition did not differ (p>0.05) among the groups, milk yield was increased by 10 per cent with total replacement of wheat bran in concentrate mixture with of black gram foliage. The economics of milk production calculated as feed cost per kg milk yield (INR 10.61 vs 7.98) was reduced by complete replacement of wheat bran with black gram foliage. Conclusion: Black gram foliage could be used as complete replacement for wheat bran in concentrate mixture of dairy cows in formulating least cost ration for economic milk production in small holders' animal production.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5A
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• pp.299-305
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• 2012

The objective of this paper is to obtain the basic data in order to develop an eco-friendly concrete through evaluation on the properties of polymer cement mortar and concrete using PVAc (Polyvinyl Acetate), as a kind of water-soluble polymer. For this purpose, the physical properties of cement mortar and concrete which does not contain the PVAc as the control batch were compared and analyzed with those using the PVAc. And then, the replacement amount of the PVAc was 3%, 6%, 9% and 12% by binder, respectively. And also, the properties of concrete using the PVAc were evaluated, by adding an antifoaming agent in order to control the air contents increasing with an increase of amount of polymer usage. As a result, in the case of polymer cement mortar using the PVAc, it presented that the compressive strength reduced, while the performance of flexural strength and drying shrinkage increased. When the replacement of the PVAc was 6% within concrete, the compressive, tensile, flexural strength and elastic modulus were increased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.2107-2124
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• 2013

The inspections that are being done on current bridges in our country are made to go through a process of being recorded on the management system and then converted by the computer. This has deteriorated the credibility of manual-analog types of data, inefficient care of information, and produced potential problems of the structures of bridges through subjective evaluations. In order to solve these troubles, this research has aimed at effectiveness, management, and convenience so that the inspector at the actual scene of the bridge structures will be able to achieve the primary purpose of infrastructure safety through precise supervision. To assist this, this study has suggested a state of the art IT intellectual management system that has applied RFID. This system has been designed to decrease the inspecting time on the actual scene, which will provide more time for efficient inspection and by using the converted DB, managing and utilizing high quality data will come naturally and through the objective evaluation, it will be possible to make exact judgments of the structures of the bridge. Also, regardless of the location, it has been found that the work performance was excellent through highly effective management.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.7
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• pp.713-721
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• 2005

A marine diesel engine should realize optimal operation efficiency while reducing NOx, PM (Particulate Matters) and other emissions. Fuel injection systems that use electronic control can become an effective means of achieving that objective. However. it still needs some accurate and instant information in order to bring its ability into full potential while sailing on the sea. The important information of them are a shaft torque and continuous combustion pressures of all cylinders. The shaft torque and the propeller thrust described in this paper are measured at an intermediate shaft by using a unique principle that one of two electromagnet coils oscillates a vibrating strip which the length changes with force and the other coil picks up the change of the frequency of the vibrating strip. For further reference, the shaft power meter multiplied the torque by the shaft revolution has already had about 750 sets of sales performance. The research presented in this paper started about ten years ago and is concerned with the development of a combustion pressure sensor that uses the same principle. Recently, the pressure sensor which bears continuous operation has been developed after a hard struggle, that is, the system that consists of a shaft horsepower meter, a propeller thrust meter and a combustion pressure sensor has been completed and has been shown to be reliable. This paper describes the configuration of this system, the material of the combustion pressure sensor, the principle of that, and the improving point of the sensor, and, we finally consider the use of this system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.511-519
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• 2013

Switching controllers for active magnetic bearings are claimed to minimize the copper losses because they do not use bias currents. In this study, we compare the performances of the switching controller with those of the widely used proportional-derivative (PD) controller. The PD controller is combined with a synchronous notch filter to reduce the effect of the unbalance disturbance. For a fair and objective comparison, the PD controller is designed systematically. The switching controller is designed so that the dynamics of the two controllers are almost identical. A system model is developed. This model includes the flexible modes of the rotor and the dynamics of the sensors and amplifiers. The simulation results show that the switching controller indeed reduces the copper loss at lower speeds. However, it fails to operate around the speed close to the bending mode of the rotor.

• Journal of Environmental Impact Assessment
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• v.14 no.6
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• pp.403-413
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• 2005

The environmental conservation-targeted zoning in urban planning process has been functioned as securing a ecological core in urban green spaces management. Hence, the designation of conservation zones in land use planning is considered as a key task to achieve the sustainability of urban planning. The recently introduced pre-environmental review system for the proposed urban plan, by which the conservative measures for urban ecosystem and landscape are suggested in aspect of environmental impact mitigation, has played an active role in enhancing the environmental performance degraded by wide range of development pressure. This study is aimed at drawing out of objective criteria for designation of environmental conservation zones, which can be applied to urban planning establishment and also to environmental assessment process. To achieve this goal, the study adopted the following methods; pre-study review, analysis of existing official opinion statements released by the Ministry of Environment, contents analysis of related laws, and experts' panel discussions on the finally arranged criteria. The results of this research can be summarized as follows: First, the total criteria of 48 are drown out with categorizing into environment-ecological and socio-cultural sectosr. Second, the environment-ecological part is composed of 33 criteria such as vegetation, animal, geomorphology, watershed, environmental land suitability, and etc. Here, the Degree of Ecological Function, Degree of Environmental Land Suitability, and Vegetation Map are mainly utilized. Third, the 15 socio-cultural criteria relating to the history, social ecology and landscape have such components as forest around relics, Seo-won(school), castle, tomb, landmark, skyline, natural landscape, and etc. Forth, these individual criteria can be applied to designation of each conservation zones among total of 11 conservation areas(or districts).

• Journal of Environmental Impact Assessment
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• v.23 no.6
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• pp.445-452
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• 2014

The objective of this study was to propose the best methodology for estimating soil organic carbon stocks during environmental assessment for development projects. We compared three methodologies which were developed by Korea Environment Corporation(2010), Korea Forest Research Institute (2006), and Jin-Hyun Jung (1998). We found that the methodology developed by Jin-Hyun Jung (1998) shows the worst performance and the methodology of Korea Forest Research Institute (2006) does not reflect a variety of soil types and land use characteristics shown in development project plans. Therefore, we propose that the methodology developed by Korea Environment Corporation (2010) is the most reasonable one because it is internationally accepted and used for local governments to make the inventory of greenhouse gases as well as to set up its reduction strategy.