• Journal of the Korean Society for Railway
• /
• v.10 no.6
• /
• pp.742-750
• /
• 2007

This paper presents a mathematical model for a double-fleet operation in Korean high speed rail (HSR). KORAIL has a plan to launch new HSR units in 2010, which are composed of 10 railcars. The double-fleet operation assigns a single-unit or two-unit fleet to a segment, accommodating demand fluctuation. The proposed model assumes stochastic demand and uses chance-constrained constraints to assure a preset service level. It can be used in the tactical planning stage of the rail management as it includes several real-world conditions, such as the capacities of the infra-structures and operational procedures. In the solution approach, the expected revenue in the objective function is linearized by using expected marginal revenue, and the chance-constrained constraints are linearized by assuming that demands are normally distributed. Subsequently, the model can be solved by a mixed-integer linear programming solver fur small size problems. The test results of the model applied to Friday morning train schedules for one month sample data from KTX operation in 2004 shows that the proposed model could be utilized to determine the effectiveness of double-fleet operation, which could significantly increase the expected profit and seat utilization rates when properly maneuvered.

• Wind and Structures
• /
• v.21 no.2
• /
• pp.159-182
• /
• 2015

This study focuses on the amplitude dependency of damping of tall structures by the random decrement technique (RDT). Many researchers have adopted RDT to establish the amplitude dependency of damping ratios in super-tall buildings under strong wind loads. In this study, a series of simulated examples were analyzed to examine the reliability of this method. Results show that damping ratios increase as vibration amplitudes increase in several cases; however, the damping ratios in the simulated signals were preset as constants. This finding reveals that this method and the derived amplitude-dependent damping ratio characteristics are unreliable. Moreover, this method would obviously yield misleading results if the simulated signals contain Gaussian white noise. Full-scale measurements on a super-tall building were conducted during four typhoons, and the recorded data were analyzed to observe the amplitude dependency of damping ratio. Relatively wide scatter is observed in the resulting damping ratios, and the damping ratios do not appear to have an obvious nonlinear relationship with vibration amplitude. Numerical simulation and field measurement results indicate that the widely-used method for establishing the amplitude-dependent damping characteristics of super-tall buildings and the conclusions derived from it might be questionable at the least. More field-measured data must be collected under strong wind loads, and the damping characteristics of super-tall buildings should be investigated further.

• Journal of Communications and Networks
• /
• v.2 no.1
• /
• pp.58-68
• /
• 2000

In this paper we introduce the correlation-aided distributed sample acquisition (CDSA) scheme for fast cell search in IMT-2000 W-CDMA cellular system. The proposed scheme incorporates the state symbol correlation process into the comparison-correction based synchronization process of the original DSA scheme to enable fast acquisition even under very poor channel environment. for its realization, each mobile station (MS) has to store in its memory a set of state sample sequences. which are determined by the long-period scrambling sequences used in the system and the sampling interval of the state samples. CDSA based cell search is carried out in two stages : First, the MS first acquires the slot timing by using the primary synch code (PSC) and then identifies the igniter code which conveys the state samples of the current cell . Secondly. the MS identifies the scrambling code and frame timing by taking the comparison-correction based synchronization approach and, if the identification is not done satisfactorily within preset time. it initiates the state symbol correlation process which correlates the received symbol sequence with the pre-stored state sample sequences for a successful identification. As the state symbol SNR is relatively high. the state symbol correlation process enables reliable synchronization even in very low chip-SNR environment. Simulation results show that the proposed CDSA scheme outperforms the 3GPP 3-step approach, requiring the signal power of about 7 dB less for achieving the same acquisition time performance in low-SNR environments. Furthermore, it turns out very robust in the typical synchronization environment where large frequency offset exists.

• Journal of the Korean Institute of Gas
• /
• v.2 no.3
• /
• pp.88-95
• /
• 1998

Vibration analysis of rotating machinery can give an indication of possible faults thus allowing maintenance before further damage occurs. Current predictive maintenance system installed in Pyung-tak has the ability to diagnose the mechanical problems within the LNG Pump when the vibration exceeds preset overall alarm levels. In this study, LNG pump auto-diagnosis system based upon Windows NT and DSP Board is developed. This system analysis velocity signal acquired from dual accelerometer input monitor system to diagnose pump condition. Many plots which display machine condition are shown and features of vibration are stored in every time. If the fault is found, the system diagnoses automatically using expert system and trend monitoring. Operator checks pump condition intuitively using personal computer monitor.

• Journal of Environmental Science International
• /
• v.18 no.1
• /
• pp.99-111
• /
• 2009

In this study vegetation structure was monitored focusing on slanting surface of stream for the purpose of developing a management plan and ecological restoration of small stream in Paju. The study was conducted by types of geographical structure, yearly flora, naturalization rate changes, actual vegetation changes, plant community changes. Slope area of small stream in Paju was varied in the slope range of $10{\sim}35^{\circ}$. The survey results of yearly flora showed that 37 species appeared in 2000, 55 species in 2001, 95 species in 2002, and 125 species in 2003. Therefore, the trend of continuous increase of flora each year was observed. In the case of yearly changes of actual vegetation, indigenous wetland herb community including Phragmites communis$(19.99%{\rightarrow}18.42%{\rightarrow}19.60%)$ did not show substantial changes in the area, while the influence of controlled flora such as Humulus scandens$(8.86%{\rightarrow}5.26%{\rightarrow}9.73%)$, and Ambrosia artemisiifolia$(1.06%{\rightarrow}1.43%{\rightarrow}6.93%)$ were increased. The vegetation structure investigated by 18 preset belt-transects also indicated that Phragmites communis and Miscanthus sacchariflorus were maintaining the status or decreasing the population, while the population of Humulus scandens, Ambrosia artemisiifolia, Setaria viridis, and Erigeron canadensis were greatly increased. Our proposal management to restore ecology is as follows: first, preservation and restoration of Phragmites communis landscape; second, restoration of potential stream vegetation community; third, selection and removal of controlled plants.

• Journal of IKEEE
• /
• v.24 no.2
• /
• pp.559-569
• /
• 2020

One of the deep-running algorithms, CNN's artificial intelligence application uses off-chip memory to store data on the Convolution Layer. DMA can reduce processor load at every data transfer. It can also reduce application performance degradation by varying the order in which data from the Convolution layer is transmitted to the global buffer of the accelerator. For basic layouts with continuous memory addresses, SG-DMA showed about 3.4 times performance improvement in pre-setting DMA compared to using ordinaly DMA, and for Ideal layouts with discontinuous memory addresses, the ordinal DMA was about 1396 cycles faster than SG-DMA. Experiments have shown that a combination of memory data layout and DMA can reduce the DMA preset load by about 86 percent.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.18 no.2
• /
• pp.33-48
• /
• 2018

In this paper, we characterise the joint interference alignment and power allocation strategies for a K-user multicell multiple-input multiple-output (MIMO) Gaussian interference channel. We consider a MIMO interference channel with a blind interference alignment through staggered antenna switching on the receiver. We explore the power allocation and the feasibility condition for cooperative cell-edge (CE) mobile users (MUs) by assuming that the channel state information is unknown. The new insight behind the transmission strategy of the proposed scheme is premeditated (randomly generated transmission strategy) and partial cooperative CE MUs, where the transmitter is equipped with a conventional antenna, the receiver is equipped with a reconfigurable multimode antenna (staggered antenna switching pattern), and the receiver switches between preset T modes. Our proposed scheme assists and aligns the desired and interference signals to cancel the common interference signals, since the received signal must have a corresponding independent signal subspace. The sum capacity for a K-user multicell MIMO Gaussian interference channel with reconfigurable multimode antennas is completely characterised.

• Polymer(Korea)
• /
• v.26 no.2
• /
• pp.227-236
• /
• 2002

The structure of pregel state in thermoreversible poly(vinylidene fluoride)(PVDF) /propylene carbonate(PC) system was investigated by laser light scattering. It was found that the PVDF chain did not exist as a separate chain even in a very dilute concentration(i.e. 100 times more dilute than the gel formation concentration) but as a large spherical aggregate with the radius of gyration $R_G$, of 232 nm and the effective hydrodynamic radius $R_H$= of 407 nm at $40^{\circ}C$. Based upon experimental results such as $R_H/R_G$=ratio of 1.75 and the pattern of scattering intensity with a minimum, a core-shell type sphere model was suggested as a structure of the aggregate. According to this model, the radius of core part was estimated as 215 nm, the shell thickness as 192 nm, and the ratio of monomer density of the shell part to that of the core part as about 0.075.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.22 no.6
• /
• pp.861-866
• /
• 2018

In OLED (Organic Light-Emitting Diode) manufacturing, the aging process increases the manufacturing efficiency and measures the correction value to correct the aging. The correction value for correcting the aging of the OLED can be applied to the driving signal. The OLED aging process measures the current after outputting the light for a predetermined time according to the preset driving signal and temperature. In the OLED manufacturing process, aging is applied for non-uniformity by deposition and temperature. This time has little effect on OLED efficiency reduction. Heating devices and signal generation systems are required to create the conditions necessary for aging. The results measured by the heating system and signal generation system can be used as a basis for evaluating power requirements, uniformity and efficiency in OLED manufacturing. In this paper, we propose and implement a configuration for interlocking the driving signal generation and heating system for practical OLED aging correction.

• Archives of Plastic Surgery
• /
• v.44 no.1
• /
• pp.5-11
• /
• 2017

Background Conscious sedation has been widely utilized in plastic surgery. However, inadequate research has been published evaluating adequate drug dosage and depth of sedation. In clinical practice, sedation is often inadequate or accompanied by complications when sedatives are administered according to body weight alone. The purpose of this study was to identify variables influencing the depth of sedation during conscious sedation for plastic surgery. Methods This prospective study evaluated 97 patients who underwent plastic surgical procedures under conscious sedation. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatinine, and glucose levels were measured. Midazolam and ketamine were administered intravenously according to a preset protocol. Bispectral index (BIS) recordings were obtained to evaluate the depth of sedation 4, 10, 15, and 20 minutes after midazolam administration. Associations between variables and the BIS were assessed using multiple regression analysis. Results Alcohol intake and female sex were positively associated with the mean BIS (P<0.01). Age was negatively associated with the mean BIS (P<0.01). Body mass index (P=0.263), creatinine clearance (P=0.832), smoking history (P=0.398), glucose (P=0.718), AST (P=0.729), and ALT (P=0.423) were not associated with the BIS. Conclusions Older patients tended to have a greater depth of sedation, whereas females and patients with greater alcohol intake had a shallower depth of sedation. Thus, precise dose adjustments of sedatives, accounting for not only weight but also age, sex, and alcohol consumption, are required to achieve safe, effective, and predictable conscious sedation.