• Journal of The Korean Association of Information Education
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• v.24 no.4
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• pp.401-412
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• 2020

Team-based programming methods are widely applied to solve various difficulties that pre-service teachers experience in the programming lessons. To prepare effective collaboration strategies necessary for them, it is necessary to analyze various collaborative factors that affect learners' programming competencies. Therefore, in this article, a questionnaire survey was conducted by dividing learners' collaboration factors into individual and team competencies, and the relationship between learners' programming competencies was analyzed. As a result of the verification, the program design competency showed significant results in all elements of the learner's personal competency, team techniques such as data sharing skills necessary for collaboration, and team collaboration. It was analyzed that an individual's understanding of learning and team collaboration influenced the program implementation competency. In addition, the group with relatively high team technique showed significant differences in programming competence, interest, and satisfaction. Accordingly, by linking meaningful factors related to individual and team competencies according to the programming process, a collaborative strategy practically necessary for pre-service teachers was suggested.

• Journal of The Korean Society of Grassland and Forage Science
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• v.16 no.1
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• pp.47-52
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• 1996

To investigate the effects of phosphate($P_2O_5$) fertilization levels on the dry matter(DM) yield, nutrition yield, and $P_2O_5$ efficiency of forages in mixed sward of alfalfa-grasses, a field experiment arranged by randomized complete block design with five treatments(0, 50, 100, 150 and 200kg $P_2O_5$/ha) was conducted at Livestock Experiment Station in Suwon, September, 1990 to Feb~ary, 1993. During two years, average DM yields of forages increased as $P_2O_5$ fertilization level was increased, but no significant difference was found between DM 10,754kg of $P_2O_5$ 150kg/ha and DM 10,845kg of $P_2O_5$ 200kg/ha. Cmde protein and energy productivity of forages increased as $P_2O_5$ fertilization level was increased, and the increasing degree was highest between $P_2O_5$ l00kg and 150kg/ha feriilization. With increasing $P_2O_5$ fertilization, mineral contents tended to increase in P, K and WCa+ Mg equivalent ratio, but not to be regular in the other elements. Efficiency of $P_2O_5$ was highest at $P_2O_5$ 150kg/ha fertilization, which produced DM 12.8kg. net energy lactation 75.4MJ. starch equivalent 6.lkStE, and total digestible nutrients 8.6kg per Ikg $P_2O_5$.

• Korean Journal of Ichthyology
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• v.24 no.4
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• pp.263-271
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• 2012

A female preference is a potentially complex function relating variation in multiple male traits with her probability of accepting the most optimal individuals as a mate. If mate preference is dominantly driven by additive fitness benefits, different females tend to be congruent in the decision of choice, whereas females will not necessarily share their mate preferences if non-additive benefits more strongly operate. Here, a sequential blocked design ($4{\times}4$) was applied to experimentally assess the relative contribution of additive and non-additive components to the female mate preference with Korean rosy bitterling, Rhodeus uyekii. In a total of 48 single stimulus presentations, behavioral elements of courtship activities were analyzed to derive the 'index of female preference'. Females showed a clear preference for males with more elaborate carotenoid colors, but mated randomly with respect to male body size and other color patterns. However, they were not individually consistent in their choice of mates, suggesting that non-additive components probably contribute to the evolution of female preference.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.2
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• pp.3-12
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• 2001

This paper presents the proposed methods of DE (distinct element) modelling to estimate the stability of tunnels in jointed rock masses. First, the criterion to select the joint set(s) contributed to the discontinuous behaviour in a tunnel section is proposed. Selected joint set(s) is(are) considered to form the edges of distinct elements (rock blocks) and the others to modify the elastic properties of rock blocks. The complex DE model with the average and the deviation of joint orientation and joint length for each joint set was compared to the simple model with only the average of joint orientation and the assumption that joint length is infinite. As a result, the latter is suitable to the purpose of tunnel design because it can show the consistent behaviour of a jointed rock mass such as the locally discontinuous failure and the global anisotropic behaviour.

• Journal of The Korean Society of Grassland and Forage Science
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• v.16 no.2
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• pp.121-126
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• 1996

To investigate the effects of potassium($K_2O$) fertilization levels on the dry matter(DM) yield, nutrition yield, and $K_2O$ efficiency of forages in mixed sward of alfalfa-grasses, a field experiment arranged by randomized complete block design with five treatments(0, 60, 120, 180 and 240kg $K_2O$/ha) was conducted at National Livestock Research Institute in Suwon, September, 1990 to February, 1993. During two years, average DM yields of forage increased as $K_2O$ fertilization level was increased, but no significant difference was found between DM 10,617kg of $K_2O$180kgha and DM 10,845kg of $K_2O$ 240kg/ha. Crude protein and energy productivity of forages increased as $K_2O$ fertilization level was increased, and the increasing degree was highest between $K_2O$ 120kg and 180kg/ha fertilization. With increasing $K_2O$ fertilization, mineral contents tended to increase in K and WCa+Mg equivalent ratios, to decrease in Mg, but not to be regular in the other elements. Efficiency of $K_2O$ was relatively high at $K_2O$ 180kgha fertilization, which produced DM 12.2kg, net energy lactation 67.3M.J, starch equivalent 6.2kStE and total digestible nutrients 7.6kg per Ikg $K_2O$. Therefore, potassium($K_2O$) fertilization levels must be applied with I8Okg/ha for a reasonable management in mixed sward of alfalfa-grasses.

• Journal of the Korean Solar Energy Society
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• v.40 no.2
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• pp.25-36
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• 2020

The Korean government has a plan to mandate zero-energy buildings in 2020 for public and 2025 for private buildings. In order to design a zero-energy building, insulation and airtightness, which are the most basic elements of passive house technology, are required, and the government has been accomplished this through step-by-step strengthening of related standards. In passive house with high thermal insulation and airtightness performance, the heat introduced into the building through solar radiation can be stored for a long time to keep the inside warm during winter. On the other hand, during summer, heat introduced into the building cannot be easily released to outside, so it is necessary to actively block solar radiation and high temperature outdoor air to prevent an increase of indoor temperature. Therefore, this study aims to derive an appropriate operation condition of passive house to maintain the indoor temperature at an suitable level according to the ventilation methods and solar shading conditions. As a result, under the conditions that the outdoor temperature was 28℃ or less, the ventilation using a heat recovery ventilation system at daytime and natural ventilation at nighttime were selected for the most appropriate operation method. In addition, in the case of solar shading, it was found that blocking solar radiation at daytime using the blind and open the blind at nighttime to ensure natural ventilation were selected for the most appropriate solar shading condition.

• Geotechnical Engineering
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• v.2 no.3
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• pp.51-66
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• 1986

The design of fabric reinforced retaining wall structure was discussed in this article. It was confirmed that the reinforced retaining earth wall which was designed by new theoretical formulae developed this time was stable structurally and economically. The plastic fabric filter which was placed in layers behind the facing element reduced the lateral earth pressure on the wall elements in comparison with a conventional retaining earth walls. The reinforcing characteristics of earth wall was governed by the spacing of fabric layers, effective length of fabrics, particle distribution and compaction, and thus it is essential that, in the construction field, the reinforcing strips should be selected in order to develop the maximum friction forces bet.eon soil and fabric filters. The maximum tensile stress developed from the reinforcing strips was appeared at a little far distance from the back of skin element and it was not well agreed with the Rankine's theory but distributed well as a symmetrical shape against the point of the maximum tensile stress. The total length of the different layers should be sufficient so that the tension in the fabric strip could be transferred to the backfill material. Also the total stability of reinforced earth wall should be checked with respect to a failure surface which extended blond the different lathers.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.409-412
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• 2004

Over last decade extensive researches have been undertaken on the strength behaviour of Fiber Reinforced Concrete(FRC) structures. But the use of Ultra-High Strength Steel Fiber Cementitious Concrete Composites is in its infancy and there is a few experiments, analysis method and design criteria on the structural elements constructed with this new generation material which compressive strength is over 150 MPa and characteristic behaviour on the failure status is ductile. The objective of this paper is to investigate and analyze the behaviour of reinforced rectangular structural members constructed with ultra high performance cementitious composites (UHPCC). This material is known as reactive powder concrete (RPC) mixed with domestic materials and its compressive strength is over 150MP. The variables of test specimens were shear span ratio, reinforcement ratio and fiber quantity. Even if there were no shear stirrups in test specimens, most influential variable to determine the failure mode between shear and flexural action was proved to be shear span ratio. The characteristics of ultra high-strength concrete is basically brittle, but due to the steel fiber reinforcement behaviour of this structure member became ductile after the peak load. As a result of the test, the stress block of compressive zone could be defined. The proposed analytical calculation of internal force capacity based by plastic analysis gave a good prediction for the shear and flexural strength of specimens. The numerical verification of the finite element model which constitutive law developed for Mode I fracture of fiber reinforced concrete correctly captured the overall behaviour of the specimens tested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.715-720
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• 2016

This paper proposes a PWM (Pulse Width Modulation) voltage mode DC-DC step-up converter for portable devices. The converter, which is operated with a 1 MHz switching frequency, is capable of reducing the mounting area of passive devices, such as inductor and capacitor, and is suitable for compact mobile products. This step-up converter consists of a power stage and a control block. The circuit elements of the power stage are an inductor, output capacitor, MOS transistors Meanwhile, control block consist of OPAMP (operational amplifier), BGR (band gap reference), soft-start, hysteresis comparator, and non-overlap driver and some protection circuits (OVP, TSD, UVLO). The hysteresis comparator and non-overlapping drivers reduce the output ripple and the effects of noise to improve safety. The proposed step-up converter was designed and verified in Magnachip/Hynix 0.18um 1-poly, 6-metal CMOS process technology. The output voltage was 5 V with a 3.3 V input voltage, output current of 100 mA, output ripple less than 1% of the output voltage, and a switching frequency of 1 MHz. These designed DC-DC step-up converters could be applied to the Personal Digital Assistants(PDA), cellular Phones, Laptop Computer, etc.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2747-2753
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• 2011

In this paper, a PWM current-mode DC-DC boost converter for mobile phone flash application has been proposed. The converter which is operated with 5 Mhz high switching frequency is capable of reducing mounting area of passive devices such as inductor and capacitor, consequently is suitable for compact mobile phones. This boost converter consists of a power stage and a control block. Circuit elements of the power stage are inductor, output capacitor, MOS transistors and feedback resistors. Meanwhile, the control block consists of pulse width modulator, error amplifier, oscillator etc. Proposed boost converter has been designed and verified in a $0.5\;{\mu}m$ 1-poly 2-metal CMOS process technology. Simulation results show that the output voltage is 4.26 V in 3.7 V input voltage, output current 100 mA which is larger than 25 ~ 50 mA in conventional 500 Khz driven converter when the duty ratio is 0.15.