• Journal of Advanced Navigation Technology
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• v.10 no.2
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• pp.138-144
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• 2006

In this paper, dual mode FET mixer for WiBro and wireless LAN(WLAN) applications has been designed in the form of dual gate FET mixer by using the cascode structure of two single gate pHEMTs. The designed dual gate mixer has been optimized to have variable conversion gain for WiBro and WLAN applications in order to save dc power consumption. The LO to RF isolation of the designed mixer is more than 20dB from 2.3GHz to 2.5GHz band. With the LO power of 0dBm and RF power of -50dBm, the mixer shows 15dB conversion gain. When RF power increases from -50dBm to -20dBm, the conversion gain decreases to -2dB from 15dB with bias change. The variable conversion gain has several advantages. It can reduce the high dynamic range requirement of AGC burden at IF stage. Also, it can save the dc power dissipation of mixer up to 90%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.2
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• pp.303-312
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• 2009

In this paper, we design and fabricate a disk sector antenna fed by CPW fur UWB communications. Also, we insert a rectangular slit on the arc-edge of the disk sector antenna. Then, the antenna has the directivity of E-면. In order to design the antenna, the input impedance is matched with the feed line of $50{\Omega}$ as varying the physical antenna parameters, which are the radius, the flare angle of disk sector, the length of ground, and the length of ground comer near by feed tine. Dimension of the antenna designed for UWB communication is $72mm{\times}26mm$ and bandwidth through computer simulation is $3{\sim}13GHz$. From the measured results, the bandwidth is $1.98{\sim}11GHz$. Return loss and gain of the fabricated antenna are -50.38dB, 1.34dBi at 3.5GHz, -12.27dB, 3.35dBi at 5.5GHz, -23.2dB, 3.8dBi at 8GHz and -16.17dB, 5.2dBi at 10GHz, respectively.

• KSBB Journal
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• v.19 no.4
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• pp.284-287
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• 2004

The purpose of this study was to find an optimum extraction condition of acanthoside-D from acanthopanax cortex with supercritical carbon dioxide as a solvent. In this effort, effects of the extraction conditions including pressure, temperature and presence or absence of a cosolvent on the extraction efficiency were investigated. The ethanol, water or 50% methanol was used as a cosolvent whilst the operating pressure ranged from 200 bar to 300 bar. The acanthoside-D concentrations were determined by means of HPLC equipped with a UV detector. From the results, it was observed that increase of higher pressure led to the higher extraction efficiency. Further, water was found to be the best cosolvent among the entrainers tested.

• Korean Journal of Organic Agriculture
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• v.8 no.3
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• pp.111-120
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• 2000

In this study, by-products of rice bran, rice hull, bean curd dregs and food waste were fermented with different ratios of 26, 26, 34 and 14% respectively and the experimental diets were prepared mixing it with various ratios of commercial diets (fermented feed commercial feed : A 80 : 20, B 70 : 30, C 60 : 40, D 50:50). In Experiment I, feed intake, nutrients digestibilities and nitrogen retention were investigated and body weight gain in Experiment 1. For chemical composition of experimental diets, crude protein contents were 13.73, 13.78, 14.45 and 15.14% in A, B, C and D respectively and the contents of crude fat and crude fiber were highest in A as 8.66 and 27.82% respectively. 2. Dry hurler intakes were significantly higher (P<0.05) in A(362.06g/d) and C(358.49g/d) than B and D. Intakes of crude protein and crude fat were not significantly different (P>0.05) among treatments however those of crude fiber and crude ash were significantly higher (P>0.05) in A(101.47g/d). 3. Dry matter digestibilities in the range of 53.38∼68.81% in all treatments have shown the highest value in C of 60% fermented feed plus 40% commercial diet but the lowest in A of 80% of fermented feed plus 20% commercial diet (P<0.05). 59.85% of digestibility of crude protein in A was also lowest among all treatments (p<0.05), 4. 8.47g/d of nitrogen intake in C was recorded highest (P<0.05) however the highest nitrogen retention was marked in B of 50% fermented feed plus 50% of commercial diet due mainly to lower excretion of nitrogen through feces. 5. The data of live weight gain in Experiment II has not been shown as a result since the proper daily gain of body weight was achieved only in D as 88.89g/d and the goats in other treatments have shown frequent diarrhea. However, neglecting the animals with diarrhea, higher amounts of concentrates in the diets (C and D) showed the tendency of higher weight gain. 6. In this study, feeding 60% fermented feed manufactured with domestic agricultural by-products of rice bran, rice hull, bean curd dregs and food waste to Korean native goats have shown satisfactory results of intake and digestibility and it indicates that utilization of domestic agricultural by-products in goats could be improved by the process of fermentation. However it's effects on body weight gain and nitrogen retention were below than expected. Different sources of feedstuff for fermentation may result in different performances of animals. However, to draw overall conclusion from this study, 50∼60% of fermented feed can be recommended in the case of mixing with concentrates.

• Journal of Technology Innovation
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• v.17 no.1
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• pp.149-177
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• 2009

Today, the phase of modem war is very different from past war. That is, the winning of war depends on the ability to obtain information and high technology. The purposes of this research are to propose an effective R&D governance model in national defense sector and to present R&D strategy for obtaining core national defense technology. As a part of collaborative innovation, the strategy to exchange R&D results actively between the defense sector and the private sector will be discussed. The main contribution of this research is dearly defining the concept of R&D governance in national defense sector and applying it to an actual case. The national defense R&D governance model proposed in this paper is based on the characteristics of national defense R&D which are different from other industries. The analysis of business success factors for national defense R&D through the T-50 case study is presented in detail. The T-50 case study reveals the importance of strategic intent, core technology knowledge base, organizational structure, and project management.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.10
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• pp.1492-1497
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• 2005

The goal of the trial was to evaluate the effects of ractopamine (20 ppm in the ration) given pregnant sows during three different pregnancy stages (T1: 25 to 50 d; T2: 50 to 80 d; T3: 25 to 80 d of gestation, and T4: control-no ractopamine) on fetal muscle development (through counts of the number of fibers of the semitendinosus muscle), on the growth and carcass characteristics of the progeny. Forty eight weaned piglets (12 per treatment) were assessed for number of muscle fibers, while performance and carcass characteristics were evaluated on a separate 48 animals (12 per treatment) grown to 100 kg. Animals produced by sows treated from 25 to 50 d of pregnancy (T1) resulted in non-significant increase of 6.85% in the number of muscle fibers in the semitendinosus muscle when compared to animals from the control group. Performance results were significantly different (p<0.05), and animals produced by sows from the T1 group gained more weight during the growth I stage (25 to 50 kg) and during the total period (6 to 100 kg) (991 vs. 903 grams, and 844 vs. 772 grams, respectively) when compared to controls. For carcass characteristics, results showed that animals produced by the T1 group of sows were heavier at slaughter (p<0.05) when compared to the controls (T4) (100.17 vs. 93.09 kg). There was a positive correlation between number of muscle fibers and bodyweights, carcass weights, Longissimus dorsi muscle depth and dressing out (0.80, 0.86, 0.67, and 0.50, respectively). Sows treated with ractopamine between 25 to 50 d of pregnancy produced piglets that performed better and had superior carcass characteristics than those produced by untreated sows. The ractopamine used for pregnancy sows (25 to 50 d) can be indicated as a device to increase the progeny performance.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.18 no.2
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• pp.61-67
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• 1982

Optical properties of sea water were studied in the southern sea of Korea, based on ten oceanographic stations in July, 1980. Submarine daylight intensity was measured at intervals of 5m depth in the upper 70m layer by using the underwater irradiameter (Kahlsico # 268 WA 360). The mean absorption coefficients of the sea water were shown as 0.102 (0.066~0.137), 0.119 (0.069~0.154), 0.091 (0.054~.0123), and 0.095 (0.056~0.129) for clear, red, green, and blue color respectively. The transparency ranged from 13 to 25 meters (mean 17.1 m). The mean water color in this area was 3.9 (3-5) in Forel scales. The relation between absorption coefficient (k) and transparency (D) was k=1.17/D, k=2.01/D, k=1.52/D, and k=1.60/D for clear, red, green, and blue color respectively. The rates of light penetration for clear, red, green, and blue color in four different depths were computed with reference to the surface light intensity respectively. The mean rates of light penetration in proportion to depths were as follows; clear : 57.3%(5m), 20.82%(15m), 5.16%(30m), 0.94%(50m). red : 52.2%(5m), 15.99%(15m), 2.99%(30m), 0.39%(50m). green : 60.9%(5m), 24.51%(15m), 7.11%(30m), 1.56%(50m). blue : 59.4%(5m), 22.92%(15m), 6.09%(30m), 1.29%(50m).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6397-6402
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• 2015

This research was performed to review operating parameters, optimum condition and check characteristic of microbubble generation for using bubble size distribution according to venturi specification. Optimum operating condition have airflow rate 0.3 LPM, 3 bar(pressure tank) and connecting nozzle directly(without valve), it is advantageous to generate microbubble. In case of characteristic of microbubble generation according to venturi specification, effect that nozzle specification affects bubble size distribution is low impact. But considering performance aspects, when using nozzle that throat diameter 3-4 mm, $D_{50}$ are $54.98-61.19{\mu}m$(D3L15, D4L15), fraction of bubble less than $50{\mu}m$ are 0.326, 0.345. And it is superior to others. Besides, $D_{50}$ and fraction of bubble less than $50{\mu}m$ of throat length 20 mm are $49.40-54.98{\mu}m$, 0.447, respectively And nozzle that throat length 20 mm is relatively tendency to generate microbubble stably.

• Composites Research
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• v.36 no.3
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• pp.193-198
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• 2023

Currently, there are many discussions about composite materials and 3D printed composite material to weight reduction of ships. A test was conducted to confirm the applicability of the 3D printed composite material to ships and offshore structures by linking the 3D printing technology with excellent productivity and the composite material with corrosion resistance and lightweight characteristics in salt water environments. In order to apply the 3D printed composite material used in this paper to ships and offshore structures, the temperature environmental effects that can be exposed in the marine environment should be considered. Therefore, the tensile test was conducted with specimen of Carbon + Onyx, Carbon + Nylon, HSHT glass + Onyx, HSHT glass + Nylon material in low temperature (-50℃), room temperature (20℃), and high temperature (50℃) environments that can be exposed to the marine environment. As a result of the tensile test, the carbon + onyx specimen showed the highest tensile strength and the HSHT glass + onyx specimen showed the highest tensile strain. In addition, by analyzing the tested specimens, the failure mode of the 3D printed composite material specimens exposed to various temperature environments was analyzed.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.9
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• pp.1255-1262
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• 2000

A total of 80 pigs ($5.68{\pm}0.61kg$ BW; 21 d of age) were used to evaluate the effect of fat sources in weaned pigs. Pigs were allotted into five treatments based on body weight, in a completely randomized block design. Treatments consisted of diets representing different ratio between soy oil or corn oil and tallow; 1) S100 (soy oil 100%), 2) S75 (soy oil:tallow=75:25), 3) S50 (soy oil:tallow=50:50), 4) C75 (corn oil:tallow=75:25), 5) C50 (corn oil:tallow=50:50). During d 0 to 14, pigs were fed diets containing 3,400 kcal ME, 23% crude protein, 1.65 % lysine and for the period of d 15 to 28, pigs were fed diets supplying 3,400 kcal ME, 20.5% crude protein, 1.355% lysine. For d 0 to 14, a significant differences in ADG and ADFI were observed among treatments, pigs fed animal-vegetable fat blends gained more than pigs fed the S100. As tallow addition was increased from 25% to 50% replacing soy or corn oil, ADG was improved from 6.32% to 28.38%. In phase II (d 15 to 28) period, ADG, ADFI and FCR were not significantly different among treatments. For overall period (d 0 to 28), pigs fed 50% animal:50% vegetable fat blends diets consumed more feed and grew faster than pigs fed control diet and 75% vegetable oil:25% tallow groups, but the differences was not significant among treatments. Apparent DM, CP and fat digestibility were increased with time postweaning for each treatment. There were no differences in digestibilities of total amino acid during overall period. The combination of soy oil or corn oil with tallow produced slightly higher serum triglycerides (TG) and total cholesterol (TC) combination compared with the soy oil alone. In conclusion, tallow:soy (or corn) oil blends diets improved growth rate and the ratio of 50% tallow plus 50% soy (or corn) oil blends diets were favorable for growth and nutrient digestibilities of weaned pigs.