• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.33 no.4
• /
• pp.225-235
• /
• 2020

Ultrasonic investigation of damage detection has been widely used for non-destructive testing of various concrete structures. This study focuses on damage detection analysis with the aid of wave propagation in two-phase composite concrete with aggregate (inclusion) and mortar (matrix). To fabricate a realistic simulation model containing a variety of irregular aggregate shapes, the mesh generation technique using an image processing technique was proposed. Initially, the domains and boundaries of the aggregates were extracted from the digital image of a typical concrete cut-section. This enables two different domains: aggregates and mortar in heterogeneous concrete sections, and applied the grids onto these domains to discretize the model. Subsequently, finite element meshes are generated in terms of spatial and temporal requirements of the model size. For improved analysis results, all meshes are designed to be quadrilateral type, and an additional process is conducted to improve the mesh quality. With this simulation model, wave propagation analyses were conducted with a central frequency of 75 kHz of the Mexican hat incident wave. Several void damages, such as needle-shaped cracks and void-shaped holes, were artificially introduced in the model. Finally, various formats of internal damage were detected by implementing energy mapping based signal processing.

• Publications of The Korean Astronomical Society
• /
• v.30 no.3
• /
• pp.821-832
• /
• 2015

As a part of the short-period variability survey (SPVS) at Bohyunsan Optical Astronomy Observatory, we obtained time-series BV CCD images in the region of the open cluster NGC 1039 (M34). The observations were performed for 22 nights from July 29, 2008 to September 26, 2010. We also made LOAO observations for 10 days from September 18, 2009 to October 30, 2010 to confirm the small variabilties of ${\delta}$ Scuti-type variable stars. In this paper we presented the observational properties of 28 variable stars found in the region. They are seven ${\delta}$ Scuti-type variable stars, two ${\gamma}$ Doradus-type variable stars, four-teen eclipsing binary stars and five semi-long periodic or slow irregular variables, respectively. Only three variables were listed in the GCVS and the rest are newly discovered ones. We have performed multiple-frequency analysis to determine pulsation frequencies of the ${\delta}$ Scuti-type and ${\gamma}$ Doradus-type variable stars, using the discrete Fourier transform and linear least-square fitting methods. We also have derived the periods and amplitudes of 12 eclipsing binaries from the phase fitting method, and presented the light curves of all variable stars.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.38 no.3
• /
• pp.284-289
• /
• 2011

Lesch-Nyhan syndrome is a disease caused by metabolic disorder of purine. General muscle stiffness and hyposomia are shown from infancy and symptoms can include involuntary or irregular movements of arms and legs, mental retardation, and compulsive self-mutilating behaviors. Self-mutilating behaviors begin at approximately the first year or sometimes at late teens. The patients bite their lips, especially lower lip, tongue, buccal mucosa, hands and fingers. Tongue and lips can be injured or mutilated in severe cases. As the patient gets older, self-mutilating behaviors become more serious and extensive and secondary infection of injured areas is possible. Periodic soft tissue damage due to self-mutilating may evolve to cancer. Medical treatment, appliance treatment, extraction of tooth and surgical operation was attempted to control self-mutilaing behaviors. We hereby report the case of child Lesch-Nyhan syndrome patient who has self-inflicted labial damage as chief complaint. When patient was treated with conservate therapy, such as removable or fixed appliance, the frequency of labial damage could be subdued and yielded favorable results.

• International Journal of Aeronautical and Space Sciences
• /
• v.8 no.1
• /
• pp.10-20
• /
• 2007

For spacecraft attitude control, reaction wheel (RW) steering laws with more than three wheels for three-axis attitude control can be derived by using a control allocation (CA) approach.1-2 The CA technique deals with a problem of distributing a given control demand to available sets of actuators.3-4 There are many references for CA with applications to aerospace systems. For spacecraft, the control torque command for three body-fixed reference frames can be constructed by a combination of multiple wheels, usually four-wheel pyramid sets. Multi-wheel configurations can be exploited to satisfy a body-axis control torque requirement while satisfying objectives such as minimum control energy.1-2 In general, the reaction wheel steering laws determine required torque command for each wheel in the form of matrix pseudo-inverse. In general, the attitude control command is generated in the form of a feedback control. The spacecraft body angular rate measured by gyros is used to estimate angular displacement also.⁵ Combination of the body angular rate and attitude parameters such as quaternion and MRPs(Modified Rodrigues Parameters) is typically used in synthesizing the control command which should be produced by RWs.¹ The attitude sensor signals are usually corrupted by noise; gyros tend to contain errors such as drift and random noise. The attitude determination system can estimate such errors, and provide best true signals for feedback control.⁶ Even if the attitude determination system, for instance, sophisticated algorithm such as the EKF(Extended Kalman Filter) algorithm⁶, can eliminate the errors efficiently, it is quite probable that the control command still contains noise sources. The noise and/or other high frequency components in the control command would cause the wheel speed to change in an undesirable manner. The closed-loop system, governed by the feedback control law, is also directly affected by the noise due to imperfect sensor characteristics. The noise components in the sensor signal should be mitigated so that the control command is isolated from the noise effect. This can be done by adding a filter to the sensor output or preventing rapid change in the control command. Dynamic control allocation(DCA), recently studied by Härkegård, is to distribute the control command in the sense of dynamics⁴: the allocation is made over a certain time interval, not a fixed time instant. The dynamic behavior of the control command is taken into account in the course of distributing the control command. Not only the control command requirement, but also variation of the control command over a sampling interval is included in the performance criterion to be optimized. The result is a control command in the form of a finite difference equation over the given time interval.⁴ It results in a filter dynamics by taking the previous control command into account for the synthesis of current control command. Stability of the proposed dynamic control allocation (CA) approach was proved to ensure the control command is bounded at the steady-state. In this study, we extended the results presented in Ref. 4 by adding a two-step dynamic CA term in deriving the control allocation law. Also, the strict equality constraint, between the virtual and actual control inputs, is relaxed in order to construct control command with a smooth profile. The proposed DCA technique is applied to a spacecraft attitude control problem. The sensor noise and/or irregular signals, which are existent in most of spacecraft attitude sensors, can be handled effectively by the proposed approach.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.9 no.4
• /
• pp.164-172
• /
• 2004

Water temperature, salinity, the phytoplankton community and population of a marine photosynthetic ciliate, Mesodinium rubrum (=Myrionecta rubra), were monitored every 0.5-2 weeks in Gomso Bay and the Geum River Estuary from September 1999 to December 2000. Patterns of temporal variation of the M. rubrum population and phytoplankton community were compared with each other in relation to the differences in temporal fluctuation patterns of the water temperature and salinity in the two study areas. Higher population densities and more frequent blooms of M. rub rum in the Geum River Estuary than those in Gomso Bay could be due to the relatively higher nutrient input by freshwater influx in the Geum River Estuary. In the Geum River Estuary which experience more abrupt and irregular fluctuations of salinity, M. rubrum with its greater tolerance to salinity change exhibited increased dominance while neritic diatoms such as Skeletonema costatum, Asterionellopsis glacialis, A. kariana, Chaetoceros debilis, Eucampia zodiacus, Paralia sulcata, Thalassiosira pacifica, T. nordenskioeldii showed decreased dominance compared with those in Gomso Bay. Thus, it is possible that M. rubrum replaces the dominant diatom species in coastal waters where artificial modification of coast lines as in the case of Saemankeum Reclamation Project should increase the frequency as well as the absolute scale of freshwater discharges.

• The Korean Journal of Food And Nutrition
• /
• v.25 no.3
• /
• pp.599-611
• /
• 2012

The purpose of this study was to investigate the effect of food behavior on dietary food intake status and health condition based on research of food behavior and nutritional intake status of university students in the Chungnam area. The average age, height, and weight of the subject group were 22.1 years old, 174.2 cm, and 67.0 kg for the male students and 20.9 years old, 161.8 cm, and 53.4 kg for the female students, respectively. From the nutritional intake status data, the averaged daily energy intake of both groups, male and female, are lower than the dietary reference intake(KDRI), as 2,169.2 kcal and 1,846.2 kcal, males and females, respectively. The lipid intake ratio was higher than the dietary reference figure, and the carbohydrate intake ratio was determined to be in the proper range. Male students(54.6%) and female students(52.0%) of the entire subject group skipped a breakfast mainly due to insufficient time, and the time at which meals were consumed, was determined to be irregular generally. In a day, male and female students have a heavier dinner than lunch(p<0.05), respectively. Meat and fishes are preferred by the entire subject group, and the number of students, who do not eat carrot and mayonnaise(p<0.05), was determined to be the highest, of all foods surveyed. The averaged daily activity coefficient and the resting energy expenditure shows significant difference(p<0.001) between two groups; was 1.7 and 1.6 and the second was 1,404.3 kcal/day and 1,292.5 kcal/day for the male and female groups, respectively. As the number of attempting to reduce body weight(p<0.001), the amount smoking(p<0.001), or the frequency of drinking alcohol increases, BMI decreases. On the other hand, as body shape satisfaction increases, BMI increases also.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.45 no.2
• /
• pp.118-124
• /
• 2008

For forward error correction, DVB-S2, which is the digital video broadcasting forward error coding and modulation standard for satellite television, uses a system based the concatenation of BCH with LDPC inner coding. In DVB-S2 the LDPC codes are defined for 11 different code rates, which means that a DVB-S2 LDPC decoder should support multiple code rates. Seven of the 11 code rates, 3/5, 2/3, 3/4, 4/5, 5/6, 8/9, and 9/10, are regular and the rest four code rates, 1/4, 1/3, 2/5, and 1/2, are irregular. In this paper we propose a flexible decoder for the regular LDPC codes. We combined the partially parallel decoding architecture that has the advantages in the chip size, the memory efficiency, and the processing rate with Benes network to implement a DVB-S2 LDPC decoder that can support multiple code rates with a block size of 64,800 and can configure the interconnection between the variable nodes and the check nodes according to the parity-check matrix. The proposed decoder runs correctly at the frequency of 200MHz enabling 193.2Mbps decoding throughput. The area of the proposed decoder is $16.261m^2$ and the power dissipation is 198mW at a power supply voltage of 1.5V.

• Korean Journal of Community Nutrition
• /
• v.7 no.6
• /
• pp.731-740
• /
• 2002

This study was designed to identify premenstrual syndrome (PMS) and to investigate the correlation between premenstrual syndrome and nutritional intakes. The subjects of this study were 138 college women residing in Busan Metropolitan City. The subjects were asked to complete Menstrual Discomfort Questionnaire (MDQ) regarding PMS, food intake frequencies and nutritional intake. We studied the correlation between PMS symptoms and nutritional intake. The average height and weight of anemic subjects were 161.42 $\pm$ 3.50 cm and 51.87 $\pm$ 5.42 kg. The average BMI (body mass index, kg/$m^2$) was 19.92 $\pm$ 2.14 and PIBW (percent ideal body weight) were 93.02 $\pm$ 9.75%. Except for phosphorous, vitamin A and vitamin C intakes, the intake levels of all other nutrients were below the Korean RDA. The average calorie intake of the subjects was 1645.65 $\pm$ 352.63 kcal (82.2% of the Korean RDA) and iron intake of the subject was 11.06 $\pm$4.03 mg (69.1% of the Korean RDA) . The calcium and vitamin $B_6$ intakes were 512.26 $\pm$ 183.12 mg (73.1% of the Korean RDA) and 1.12 $\pm$ 0.14 mg (80.0% of the Korean RDA), respectively. With regard to their menstrual state, 45.9% subjects responded that their menstrual cycles were irregular. The frequency of PMS of the subjects was 30.2% (over 3 points) on 5 point scale (1 : no. 5 severe). The common symptoms of PMS of the subjects were pain (2.32 $\pm$ 1.01), negative effects (2.27 $\pm$ 0.87), behavioral changes (2.26 $\pm$ 0.85), water retention (2.07 $\pm$ 0.78) , arousal (1.79 $\pm$ 0.84) , autonomic reactions (1.77 $\pm$ 0.87) , lack of control (1.69 $\pm$ 0.75) and decreased concentration (1.68 $\pm$ 0.75) . There was significant correlation between all the PMS symptoms and calcium (p ＜ 0.01) , vitamin E (p ＜ 0.05) , carbohydrate (p ＜ 0.05) . This suggests that PMS represents the clinical manifestation of nutrient deficiency states especially calcium. Therefore we concluded that calcium supplementation is likely to be of benefit in relieving PMS symptoms.

• The Journal of the Korea Contents Association
• /
• v.16 no.3
• /
• pp.676-693
• /
• 2016

Although the methodology and models to assess the economic value of technology assets such as patents are being presented in various ways, there does not exist a structured assessment model which enables to objectively assess a database property's value, and thus there is a need to enhance the application feasibility of practical purposes such as licensing of DB assets, commercialization transfer, security, etc., through the establishment of the valuation model and the life-cycle decision logic. In this study, during the valuation process of DB assets, the size of customer demand group expected and the amount of demand, the size and importance of data sets, the approximate degree of database' contribution to the sales performance of a company, the life-cycle of database assets, etc. will be analyzed whether they are appropriate as input variables or not. As for most of DB assets, due to irregular updates there are hardly cases their life-cycle expires, and thus software package's persisting period, ie. 5 years, is often considered the standard. We herein propose the life-cycle estimation logic and valuation models of DB assets based on the concept of half life for DB usage frequency under the condition that DB assets' value decays and there occurs no data update over time.

• Journal of Nutrition and Health
• /
• v.9 no.1
• /
• pp.16-24
• /
• 1976

To determine patterns of preference for and consumption of milk and milk products in Seoul city, a study was conducted of 724 girls and 587 boys ranging in age from elementary school to collage level, from July to August, 1974. Findings are summarized as follows: In general, milk and milk products were liked by both children and adults. A contrasting low tendency to purchase such products was due to socioeconomics, habitual, and educational factors, as well as a lack of adequate nutritional information, especially with regard to milk. Knowledge of the value of milk as a source of calcium was lacking, especially among boys. The majority of homemakers understood that milk was nutritious, but not specifically as the best source of calcium for their families. Milk, especially in beverage form, was commonly regarded as food for the infant and small child. Grandparents would not drink it. Such a beliefe is similar to that found in under-developed or developing nations. The need for nutrition education must be emphasized. Milk and milk products are expensive foods, particularly for the low income family; but even in higher income levels, consumption was limited. Milk was consumed mostly by the younger family members, less by the older. Among the children, preference, knowledge, and concern with the nutritional value of milk increased with age of subjects. It is presumed that awareness improved with increasing length of school education. Greater frequency of milk intolerance was found with decreasing age of respondents: about 10 percent had some form of milk intolerance. This percentage will be found to be much higher in villages where milk is less familiar. This study indicated that respondents liked ice cream best of all the milk products. For beverage, they preferred cider and cola in summer, coffee and milk in winter. Smaller families consumed more milk than larger families. Household consumption of condensed milk was very low, mostly as coffeemate. Among households interviewed, as many had regular as irregular delivery of dairy milk. Average consumption ranged 0.5 to 1.5 Hop. Engel indices of these families ranged 20 to 60. Use of milk at home was very simple. Not many methods of preparation were found. The milk was used mostly as beverage. In order to improve the nutritional level of Korean children and adults who especially need additional calcium, milk and milk products are recommended as the best source of calcium. Nutrition education of children and their parents should receive greater emphasis.