• Geomechanics and Engineering
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• v.27 no.6
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• pp.551-560
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• 2021

Due to the low strength and high compressibility characteristics, the loess deposits tunnels are prone to large deformations and collapse. An accurate stability evaluation for loess deposits is of considerable significance in deformation control and safety work during tunnel construction. 37 groups of representative data based on real loess deposits cases were adopted to establish the stability evaluation model for the tunnel project in Yan'an, China. Physical and mechanical indices, including water content, cohesion, internal friction angle, elastic modulus, and poisson ratio are selected as index system on the stability level of loess. The data set is randomly divided into 80% as the training set and 20% as the test set. Firstly, principal component analysis (PCA) is used to convert the five index system to three linearly independent principal components X1, X2 and X3. Then, the principal components were used as input vectors for probabilistic neural network (PNN) to map the nonlinear relationship between the index system and stability level of loess. Furthermore, Leave-One-Out cross validation was applied for the training set to find the suitable smoothing factor. At last, the established model with the target smoothing factor 0.04 was applied for the test set, and a 100% prediction accuracy rate was obtained. This intelligent classification method for loess deposits can be easily conducted, which has wide potential applications in evaluating loess deposits.

• Journal of Preventive Medicine and Public Health
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• v.55 no.6
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• pp.549-558
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• 2022

Objectives: Poor complementary feeding practices have consistently contributed to the burden of child undernutrition in Indonesia. This study aimed to estimate the prevalence and predictors of the time of the introduction of solid, semi-solid, and soft foods (ISSSF), minimum dietary diversity (MDD), minimum meal frequency (MMF), and minimum acceptable diet (MAD). Methods: We analyzed 4804 last-born infants aged 6-23 months from the 2017 Indonesia Demographic and Health Survey, which employed multistage cluster random sampling. The outcomes were calculated based on the 2021 World Health Organization/United Nations Children's Fund guidelines. The predictors of the 4 complementary feeding indicators were assessed using multivariate Poisson regression with robust variance adjusting for potential confounders and study design. Results: The prevalence of ISSSF, MDD, MMF, and MAD was 86.1%, 54.3%, 71.8%, and 37.6%, respectively, with younger children less likely to meet 3 out of the 4 outcomes. Parental education, the presence of a birth attendant, and maternal media consumption were among the predictors of MDD and MAD. Children from families with higher income were more likely to meet MDD than those from low-income households (adjusted prevalence ratio [aPR], 1.16; 95% confidence interval [CI], 1.05 to 1.28). Living in an urban area was positively associated with MMF (aPR, 1.09; 95% CI, 1.04 to 1.15) and MAD (aPR, 1.12; 95% CI 1.02 to 1.24). In eastern regions, the prevalence of children achieving MDD and MAD was lower than in those living in Java and Bali. Conclusions: It is crucial that more attention and efforts are made to improve the recommended practices throughout Indonesia, since the prevalence of adequate complementary feeding practices remains low.

• Journal of Convergence for Information Technology
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• v.12 no.5
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• pp.15-20
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• 2022

This research studied the evaluation of reliability among the software quality characteristics: suitability, reliability, usability, portability, maintainability, performance efficiency, security, and compatibility. It proposes a quantitative evaluation of reliability in the measurement of software quality. This study introduces a method for measuring the failure rate included in maturity during reliability evaluation, which is one of the characteristics of software quality, and is a study with experimental data on how the failure rate changes depending on the form of failure data. Focusing on software testing, the failure rate was measured and compared according to the type of failure data by applying it to the software reliability growth model, focusing on the number of failures per day. The failure rate was measured around the failure time found through the 6-day test, and the failure rate was compared with the failure rate proposed by the international standard ISO/IEC 25023 using the measurement results, and the application was reviewed according to the data type.

• Geophysics and Geophysical Exploration
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• v.25 no.1
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• pp.38-43
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• 2022

In case axial symmetrical bodies with varying cross sections such as volcanic conduits and unexploded ordnance (UXO), it is efficient to approximate them by adding the response of thin disks perpendicular to the axis of symmetry. To compute the vector magnetic and magnetic gradient tensor respones by such bodies, it is necessary to derive an analytical expression of the circular disk. Therefore, in this study, we drive closed-form expressions of the vector magnetic and magnetic gradient tensor due to a circular disk. First, the vector magnetic field is obtained from the existing gravity gradient tensor using Poisson's relation where the gravity gradient tensor due to the same disk with a constant density can be transformed into a magnetic field. Then, the magnetic gradient tensor is derived by differentiating the vector magnetic field with respect to the cylindrical coordinates converted from the Cartesian coordinate system. Finally, both the vector magnetic and magnetic gradient tensors are derived using Lipschitz-Hankel type integrals based on the axial symmetry of the circular disk.

• Journal of the Korean Society of Safety
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• v.37 no.1
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• pp.70-77
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• 2022

The total number of Korean restaurants using delivery applications has substantially increased from 7.6% in 2018 to 11.2% in 2019. In 2020, the gross sales in the food delivery service market reached approximately 17 trillion won; this amount is virtually six times that in 2017 (i.e., 2 trillion won). Meanwhile, the annual average death toll of motorcycle riders increased by 3.5%, whereas the number of deaths due to other traffic accidents decreased by 8.2%. Consequently, the foregoing has become a critical social problem. Despite the continuing increase in the number of delivery riders due to the rapid expansion of the delivery industry, no appropriate safety management system has been established. Moreover, the government is experiencing difficulties in assessing the exact situation because of the absence of competent authority. In this study, fundamental data on the characteristics of delivery work and motorcycle accidents were collected through surveys and interviews; then, the influencing factors of traffic accidents were analyzed. Different influencing factors were identified: work experience as a rider; number of deliveries; whether to accept delivery requests in transit; manner of accepting delivery requests; and traffic law violations, such as speeding (for faster delivery) and running a red light. Because the motorcycle delivery industry has a relatively low job-entry barrier (i.e., special qualifications are not required), the riding skills of riders must be improved, and delivery companies must be technically developed to achieve a safe working environment. The results of this study can be utilized as fundamental data for system development or structural improvement of the delivery industry.

• Steel and Composite Structures
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• v.43 no.1
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• pp.91-106
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• 2022

This paper has focused on presenting a three dimensional theory of elasticity for free vibration of 3D-graphene foam reinforced polymer matrix composites (GrF-PMC) cylindrical panels resting on two-parameter elastic foundations. The elastic foundation is considered as a Pasternak model with adding a Shear layer to the Winkler model. The porous graphene foams possessing 3D scaffold structures have been introduced into polymers for enhancing the overall stiffness of the composite structure. Also, 3D graphene foams can distribute uniformly or non-uniformly in the shell thickness direction. The effective Young's modulus, mass density and Poisson's ratio are predicted by the rule of mixture. Three complicated equations of motion for the panel under consideration are semi-analytically solved by using 2-D differential quadrature method. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. Because of using two-dimensional generalized differential quadrature method, the present approach makes possible vibration analysis of cylindrical panels with two opposite axial edges simply supported and arbitrary boundary at the curved edges. It is explicated that 3D-GrF skeleton type and weight fraction can significantly affect the vibrational characteristics of GrF-PMC panel resting on two-parameter elastic foundations.

• Geophysics and Geophysical Exploration
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• v.25 no.2
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• pp.85-92
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• 2022

An elongated object in one direction can be approximated as a line segment. Here, the closed-form expressions of a line segment's vector magnetic and magnetic gradient tensor are required to interpret responses by a line segment. Therefore, the analytical expressions of the vector magnetic and magnetic gradient tensor are derived. The vector magnetic is converted from the existing gravity gradient tensor using Poisson's relation where the gravity gradient tensor caused by a line segment can be transformed into a vector magnetic. Then, the magnetic gradient tensor is derived by differentiating the vector magnetic with respect to each axis in the Cartesian coordinate system. The synthetic total magnetic data simulated by an iron pile on boreholes are inverted by a nonlinear inversion process so that the physical parameters of the iron pile, including the beginning point, the length, orientation, and magnetization vector are successfully estimated.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.4
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• pp.53-60
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• 2022

In a group-testing method, instead of testing a sample, for example, blood individually, a batch of samples are pooled and tested simultaneously. If the pooled test is positive (or defective), each sample is tested individually. However, if negative (or good), the test is terminated at one pooled test because all samples in the batch are negative. This paper considers a queueing system with a two-stage group-testing policy. Samples arrive at the system according to a Poisson process. The system has a single server which starts a two-stage group test in a batch whenever the number of samples in the system reaches exactly a predetermined size. In the first stage, samples are pooled and tested simultaneously. If the pooled test is negative, the test is terminated. However, if positive, the samples are divided into two equally sized subgroups and each subgroup is applied to a group test in the second stage, respectively. The server performs pooled tests and individual tests sequentially. The testing time of a sample and a batch follow general distributions, respectively. In this paper, we derive the steady-state probability generating function of the system size at an arbitrary time, applying a bulk queuing model. In addition, we present queuing performance metrics such as the offered load, output rate, allowable input rate, and mean waiting time. In numerical examples with various prevalence rates, we show that the second-stage group-testing system can be more efficient than a one-stage group-testing system or an individual-testing system in terms of the allowable input rates and the waiting time. The two-stage group-testing system considered in this paper is very simple, so it is expected to be applicable in the field of COVID-19.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.284-284
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• 2023

도시 침수의 발생과 규모는 도시 유역이 가지는 짧은 도달 시간으로 인하여 주로 시단위 이하의 짧은 지속시간의 강우의 극한 및 변동성에 따라 결정된다. 미래 기간에 대하여 도시 수문 시스템의 적정성을 평가하기 위해서는 기후변화에 따른 시단위 이하 강우의 특성을 살펴보아야한다. 그러나 기후변화 영향 평가 도구로 활용되는 기후 모형들은 대부분 일단위의 결과물을 제공하여 시단위 이하의 미세 규모 강우의 특성을 나타낼 수 없다. 이에 따라 본 연구에서는 기후 모형 모의 결과와 포아송 클러스터 강우 모형을 이용하여 미래 시단위 이하 강우 시계열을 모의하는 방법을 제안한다. 첫째로, 포아송 클러스터 기반 강우 생성 알고리즘과 폭풍우 재배열 알고리즘을 결합한 최신 모형을 선정하였다. 해당 모형은 광범위한 시간 규모에서 관측된 강우량의 주요 통계와 극값을 재현할 수 있는 모형이다. 그 다음 강우 모형에 적합시킬 관측 강우량 통계(평균, 분산, 공분산, 왜도, 우기 비율)를 계산하였다. 둘째, 강우 통계 간의 선형 관계를 도출하였다. 여기서는 클러스터에 있는 모든 관측소의 통계를 사용하여 회귀의 신뢰도를 높였다. 셋째, 강우 평균 조정을 위한 Change Factor는 제어(2000~2019년) 및 미래(2041~2070년) 기간의 기후 모형 자료를 사용하여 계산하였다. 넷째, 조정된 15분 강우 평균은 관측 평균에 Change Factor을 곱하여 계산하고 조정된 강우 평균과 통계 간의 관계를 사용하여 미래 강우 통계 세트를 추정하였다. 여러 통계 세트를 생성한 후 마지막으로 미래 통계에 강우 모형을 적합시켜 최종적으로 미래 시단위 이하 강우 시계열을 모의하였다. 이 방법은 CMIP6에 참여하는 기후 모델의 기후 예측 데이터를 사용하여 용산(415) 및 동래(940) AWS 관측소에 적용되었다. 두 관측소의 미래 강우 모의 결과, 시단위 이하 시간 규모에서 극값이 증가하는 추세를 보였다.

• Korean Journal of Clinical Pharmacy
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• v.33 no.3
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• pp.168-177
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• 2023

Background & Objectives: Fixed-dose combinations (FDCs) offer advantages in adherence and cost-effectiveness compared to free combinations (FCs), but they can also complicate the prescribing process, potentially leading to therapeutic duplication (TD). This study aimed to identify the prescribing patterns of FDCs for dyslipidemia and investigate their associated risk of TD. Methods: This was a retrospective cohort study involving drugs that included statins, using Health Insurance Review & Assessment Service-National Patient Sample (HIRA-NPS) data from 2018. The unit of analysis was a prescription claim. The primary outcome was TD. The risk ratio of TD was calculated and adjusted for patient, prescriber, and the number of cardiovascular drugs prescribed using a multivariable Poisson model. Results: Our study included 252,797 FDC prescriptions and 515,666 FC prescriptions. Of the FDC group, 46.52% were male patients and 56.21% were aged 41 to 65. Ezetimibe was included in 71.61% of the FDC group, but only 0.25% of the FC group. TD occurred in 0.18% of the FDC group, and the adjusted risk ratio of TD in FDC prescriptions compared to FC was 6. 44 (95% CI 5. 30-7. 82). Conclusions: Prescribing FDCs for dyslipidemia was associated with a higher risk of TD compared to free combinations. Despite the relatively low absolute prevalence of TD, the findings underline the necessity for strategies to mitigate this risk when prescribing FDCs for dyslipidemia. Our study suggests the potential utility of Clinical Decision Support Systems and standardizing nomenclature in reducing medication errors, providing valuable insights for clinical practice and future research.