• International Journal of Highway Engineering
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• v.15 no.5
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• pp.91-99
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• 2013

PURPOSES : This study aims at proposing the methodology for benefit evaluations in pavement maintenance methods and timings using KoPMS(Korean Pavement Management System) software which was developed for efficient pavement management. METHODS : This study classified pavement sections into 4 clusters considering AADT(Annual Average Daily Traffic) and ESAL(Equivalent Single-Axle Load) using cluster analysis and used the deterioration models in each cluster. Increased user costs due to pavement deterioration as time goes by and agent costs for maintenance were estimated. Based on deterioration model and KoPMS software, Methodology for benefit evaluation was proposed in pavement maintenance methods and with/without implementation using real pavement section data. RESULTS : This study verified that considering agent costs only would be constrained to decide pavement maintenance methods and timings, and ascertained that decision making with agent and user costs would be effective. In addition, this study revealed that pavement maintenance methods and timings can be affected by AADT and ESAL and frequent pavement maintenances can be more efficient for benefits in pavement sections with more AADT and ESAL. Also this study found that user costs would be more affected to decision making than agent costs. Moreover, Delay of conducting pavement maintenance caused increased vehicle operating costs and environmental costs because of poor conditions of pavements. CONCLUSIONS : This study proposed LCCA and benefit estimation methodology of pavement with considering agent and user costs. The results of this study can be used for baseline data of efficient pavement asset management.

• International Journal of Highway Engineering
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• v.2 no.2
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• pp.139-148
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• 2000

Currently existing Accelerated Pavement Testing (APT) systems developed in several countries have been employed mainly to test the performance of asphalt pavement. Meanwhile, the length of concrete pavement is similar to that of asphalt pavement in expressways of Korea. and is expected to increase due to its durability and compatibility to our weather condition. To meet the society's demand of having our own APT system which can examine the long-term performance of concrete pavement, a contract study to develop Korea Accelerated Loading and Environment Simulator (KALES) for concrete pavement has been performed for 3 years from 1997 through 1999. Through the project, a detailed design was Peformed for the KALES system in which the entire structure of KALES, loading mechanism, wandering mechanism, suspension system, driving system were proposed. Also in advance to design a full-scale KALES system, a sample scale model was manufactured and tested for operating motion and force distribution. It is evident that the proposed prototype KALES system will provide higher degree of traffic simulation and durable operation, based on the satisfactory fatigue analysis.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.461-480
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• 2010

This paper analyses the data collected from the $2^{nd}$ Jindo Bridge, a cable-stayed bridge in Korea that is a structural health monitoring (SHM) international test bed for advanced wireless smart sensors network (WSSN) technology. The SHM system consists of a total of 70 wireless smart sensor nodes deployed underneath of the deck, on the pylons, and on the cables to capture the vibration of the bridge excited by traffic and environmental loadings. Analysis of the data is performed in both the time and frequency domains. Modal properties of the bridge are identified using the frequency domain decomposition and the stochastic subspace identification methods based on the output-only measurements, and the results are compared with those obtained from a detailed finite element model. Tension forces for the 10 instrumented stay cables are also estimated from the ambient acceleration data and compared both with those from the initial design and with those obtained during two previous regular inspections. The results of the data analyses demonstrate that the WSSN-based SHM system performs effectively for this cable-stayed bridge, giving direct access to the physical status of the bridge.

• Journal of Preventive Medicine and Public Health
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• v.54 no.1
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• pp.55-62
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• 2021

Objectives: After heart disease, brain stroke (BS) is the second most common cause of death worldwide, underscoring the importance of understanding preventable and treatable risk factors for the outcomes of BS. This study aimed to model the survival of patients with BS in the presence of competing risks. Methods: This longitudinal study was conducted on 332 patients with a definitive diagnosis of BS. Demographic characteristics and risk factors were collected by a validated checklist. Patients' mortality status was investigated by telephone follow-up to identify deaths that may be have been caused by stroke or other factors (heart disease, diabetes, high cholesterol, etc.). Data were analyzed by the Lunn-McNeil approach at alpha=0.1. Results: Older age at diagnosis (59-68 years: adjusted hazard ratio [aHR], 2.19; 90% confidence interval [CI], 1.38 to 3.48; 69-75 years: aHR, 5.04; 90% CI, 3.25 to 7.80; ≥76 years: aHR, 5.30; 90% CI, 3.40 to 8.44), having heart disease (aHR, 1.65; 90% CI, 1.23 to 2.23), oral contraceptive pill use (women only) (aHR, 0.44; 90% CI, 0.24 to 0.78) and ischemic stroke (aHR, 0.52; 90% CI, 0.36 to 0.74) were directly related to death from BS. Older age at diagnosis (59-68 years: aHR, 21.42; 90% CI, 3.52 to 130.39; 75-69 years: aHR, 16.48; 90% CI, 2.75 to 98.69; ≥76 years: aHR, 26.03; 90% CI, 4.06 to 166.93) and rural residence (aHR, 2.30; 90% CI, 1.15 to 4.60) were directly related to death from other causes. Significant risk factors were found for both causes of death. Conclusions: BS-specific and non-BS-specific mortality had different risk factors. These findings could be utilized to prescribe optimal and specific treatment.

• Journal of Advanced Navigation Technology
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• v.25 no.1
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• pp.29-39
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• 2021

As a means of solving traffic congestion in the downtown of large city, the interest in urban air mobility (UAM) using electric vertical take-off landing personal aerial vehicle (eVTOL PAV) is increasing. eVTOL configurations that will be used for UAM are classified by lift-and-cruise, tilt rotors, tilt-wings, tilted-ducted fans, multicopters, depending on propulsion types. This study tries to perform preliminary conceptual design for a given mission profile using reverse engineering techniques by taking the multicopter type Airbus's CityAirbus as a basic model. Wetted area, lift to drag ratio, drag coefficients were calculated using the OpenVSP which is an aerodynamic analysis software. The power required for each mission section of CityAirbus were calculated, and the corresponding battery and motor were selected. Also, total weight was predicted by estimating component weights of eVTOL.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.905-910
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• 2022

Drowsy driving requires a lot of social attention because it increases the incidence of traffic accidents and leads to fatal accidents. The number of accidents caused by drowsy driving is increasing every year. Therefore, in order to solve this problem all over the world, research for measuring various biosignals is being conducted. Among them, this paper focuses on non-contact biosignal analysis. Various noises such as engine, tire, and body vibrations are generated in a running vehicle. To measure the driver's heart rate and respiration rate in a driving vehicle with a piezoelectric sensor, a sensor plate that can cushion vehicle vibrations was designed and noise generated from the vehicle was reduced. In addition, we developed a system for classifying whether the driver is sleeping or not by extracting the model using the CNN-LSTM ensemble learning technique based on the signal of the piezoelectric sensor. In order to learn the sleep state, the subject's biosignals were acquired every 30 seconds, and 797 pieces of data were comparatively analyzed.

• Journal of Internet of Things and Convergence
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• v.10 no.2
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• pp.131-135
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• 2024

In the MQTT protocol, if the retained flag of a message published by a publisher is set, the message is stored in the broker as a retained message. When a new subscriber performs a subscribe, the broker immediately sends the retained message. This allows the new subscriber to perform updates on the current state via the retained message without waiting for new messages from the publisher. However, sending retained messages can become a traffic overhead if new messages are frequently published by the publisher. This situation could be considered an overhead when new subscribers frequently subscribe. Therefore, in this paper, we propose a retained message delivery scheme by considering the characteristics of the published messages. We model the delivery and waiting actions to new subscribers from the perspective of the broker using reinforcement learning, and determine the optimal policy through Q learning algorithm. Through performance analysis, we confirm that the proposed method shows improved performance compared to existing methods.

• Geomechanics and Engineering
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• v.38 no.1
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• pp.15-28
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• 2024

The rapid development of the economy has compelled the widen of highways, and the main challenge of this undertaking lies in the uneven settlement of road embankments. Through field and numerical experiments, this study explores the deformation mechanism of shallow buried pipelines due to road widening. The utilization of Plaxis3D software, which is adapt at simulating complex engineering geological conditions, enables the simulation of the settlement of both the central and right-side road embankments. Comparing with other numerical software such as ABAQUS and COMSOL, Plaxis provided more constitutive models including HS, HSS and Hoek-Brown model. The work concludes that the uneven settlement of road cross-sections is positively correlated with the horizontal distance from the pipeline, with a maximum settlement of 73 mm observed after construction. Furthermore, based on the Winkler's assumption, theoretical settlement and stress calculation methods are established. Results indicate that the maximum difference between the calculated values of this formula and simulated values is 1.9% and 7%, respectively. Additionally, the study investigates the stress and settlement of the pipeline's top under different angles to understand its behavior under various conditions. It finds that with traffic loads applied to the new embankment, a lever effect occurs on the lower pipeline, with the fulcrum located within the central isolation zone, leading to a transition in curve type from "single peak and single valley" to "double peak and single valley." Moreover, the settlement of pipelines on both sides of the central isolation zone and the normal stress of the pipeline's top section are symmetrical.

• Journal of Korean Academy of Nursing
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• v.30 no.1
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• pp.84-97
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• 2000

The Necessity and Purpose of the Study Recently the number of patients with chronic diseases and the aged patients is increasing steadily. Furthermore, due to the expansion of health insurance system, the number of patients hospitalized in the general hospital is increasing at a surprising speed. However, hospitals urge the early discharge of the patients for the efficiencies of hospital administration, and therefore, the number of patients who must be taken care of in their home is also increasing. Homecare nursing is one of the health care service for the patients at home who require continual attention and care, and now increasing attentions are given to it as one of the professional nursing fields. However, it was almost impossible to find a study on the actual experiences of the homecare nurses written by their own language in Korea, that it also posed a great difficulty in understanding their diverse experience. Considering these situation, this study will help understanding of them, and provide the fundamental data on their experiences for making policies to develop homecare nursing. Methods of Research Phenomenological research method was employed to analyze the lived experiences of homecare nurses fundamentally. Data collection Data were collected from August 1998 to December 1998 from ten homecare nurses who worked for patients under the homecare nursing setting as model cases designated by Seoul Nurses Association and who agreed to the purpose of this study after listening to and understanding the explanation completely. The in-depth interview was carried at the time which was convenient both for the researcher and participants for one or two hours, and recovered with the approval participants. The first interview covered diverse and broad areas like the situation of homecare nursing, and their feelings and thoughts over it, and in the second and third interviews, more specific questions are asked. Data Analysis For the phenomenological analysis, contents analysis was employed. The data collected from the participants were analyzed into the following procedures according to Van Manen 's phenomenological analysis. 1) Reserve the preconception of the researcher by restricting it inside parenthesis. 2) Make a thorough observation of the lived experiences by insight process. 3) Analyze the contents (Find out the repetitive factors) 4) Interpret the essence found. 5) State the meaning of the interpretation. Results and discussion 1. Fear and expectation for the first visit. (unfamiliarity, awkwardness, anxiety, shivering) 2. Mingle with the family (feeling friendly with the family, becoming like a family member) 3. Being proud of her own know-how (learning the know-how, organizing alternatives, building up confidence) 4. Pity for the poor. (criticizing the current government, feeling ashamed, feeling anger) 5. Difficulty of constructing cooperative system with physicians (strenuousness, frustration) 6. Helplessness due to the lack of support system (difficulty to get supplies, annoyance, embarrassment by institutional restraints) 7. Anxiousness for heavy traffic and parking (annoyance, hastiness) 8. Ethical conflicts (pity for the patients and family, skepticism about lengthening life maintenance) 9. Burden for the possible accident (pressure, anxiety, conflict, physical exhaustion) 10. Establishment of identity as a professional (fulfillment, worth, joy) 11. Being distressed at other's ignorance

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.189-197
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• 2007

Concrete tunnel lining must be designed to having the fireproof performance because the lining are sometimes exposed to very high temperature due to traffic accident. Such fire temperature may cause explosion of concrete, or collapse of tunnel structure. The purpose of this study is to obtain the fundamental fireproof behavior of fire resistance-engineered cementitious composites(FR-ECC) under fire temperature in order to use the fire protection material in tunnel lining system. The present study conducted the experiment to simulate fire temperature by employing 2 types of FR-ECC and investigated experimentally the explosion and cracks in heated surface of these FR-ECC. Employed temperature curve were hydro carbon(HC, ECl) criterion, which are severe in various criterion of fire temperature. The numerical analysis is carried out the nonlinear transient heat flow analysis and verified against the experimental data. The complex features of behavior in fire conditions, such as thermal expansion, plasticity, cracking or crushing, and material properties changing with temperature are considered. By the use of analytical model, the concrete tunnel subjected to fire loads were analyzed and discussed. With comparison of current concrete materials and FR-ECC, the experimental and analytical results of FR-ECC shows the better fire resistance performance than the other.