• 전자공학회논문지CI
• /
• 제46권2호
• /
• pp.36-43
• /
• 2009

본 논문에서는 모바일 ad-hoc 무선 센서 네트워크에서 ARQ 기반 전송을 사용하는 협력도움 라우팅 프로토콜(CRARQ)을 제안한다. 제안된 CRARQ의 주요한 목적은 데이터 전송의 효율과 신뢰성을 함께 향상시키기 위함이다. 제안된 CRARQ의 주요한 특징 및 기여도는 다음과 같다. 첫째, CRARQ는 어떤 요구기반 개념을 사용하여 소스와 목적지 사이에 경로를 설정한다. 둘째, CRARQ는 설정된 경로를 따라서 엔트로피 기반 전략을 사용하여 안정된 릴레이를 선택한다. 셋째, 소스와 목적지 사이에 데이터 전송의 신뢰성을 향상시키기 위해서 ARQ 기술기반 협력전송 방법을 사용한다. 마지막으로 제안된 CRARQ의 이론적인 분석 모델을 제안 설명한다. 제안된 라우팅 프로토콜의 성능평가는 시뮬레이션과 이론적인 분석을 통하여 이루어진다. 시뮬레이션과 이론적인 분석 결과는 페킷전송 효율(PDR) 및 Outage Probability에 대한 CRARQ의 향상된 성능을 보여준다.

• Smart Structures and Systems
• /
• 제24권4호
• /
• pp.541-552
• /
• 2019

Construction development and greenhouse gas emissions have globally required a strategic management to take some steps to stain and maintain the environment. Nowadays, recycled aggregates, in particular ceramic waste, have been widely used in concrete structures due to the economic and environmentally friendly solution, requiring the knowledge of recycled concrete. Also, one of the materials used as a substitute for concrete cement is wollastonite mineral to decrease carbon dioxide (CO2) from the cement production process by reducing the concrete consumption in concrete. The purpose of this study is to investigate the effect of wollastonite on the mechanical properties and durability of conventional composite concrete, containing recycled aggregates such as compressive strength, tensile strength (Brazilian test), and durability to acidic environment. On the other hand, in order to determine the strength and durability of the concrete, 5 mixing designs including different wollastonite values and recovered aggregates including constant values have been compared to the water - cement ratio (w/c) constant in all designs. The experimental results have shown that design 5 (containing 40% wollastonite) shows only 6.1% decrease in compressive strength and 4.9% decrease in tensile strength compared to the control plane. Consequently, the use of wollastonite powder to the manufacturing of conventional structural concrete containing recycled ceramic aggregates, in addition to improving some of the properties of concrete are environmentally friendly solutions, providing natural recycling of materials.

• Clinical and Experimental Reproductive Medicine
• /
• 제48권3호
• /
• pp.262-267
• /
• 2021

Objective: Progesterone application for luteal phase support is a well-established concept in in vitro fertilization (IVF) treatment. Water-soluble subcutaneous progesterone injections have shown pregnancy rates equivalent to those observed in patients receiving vaginal administration in randomized controlled trials. Our study aimed to investigate whether the results from those pivotal trials could be reproduced in daily clinical practice in an unselected patient population. Methods: In this retrospective cohort study in non-standardized daily clinical practice, we compared 273 IVF cycles from 195 women undergoing IVF at our center for luteal phase support with vaginal administration of 200 mg of micronized progesterone three times daily or subcutaneous injection of 25 mg of progesterone per day. Results: Various patient characteristics including age, weight, height, number of oocytes, and body mass index were similar between both groups. We observed no significant differences in the clinical pregnancy rate (CPR) per treatment cycle between the subcutaneous (39.9%) and vaginal group (36.5%) (p=0.630). Covariate analysis showed significant correlations of the number of transferred embryos and the total dosage of stimulation medication with the CPR. However, after adjustment of the CPR for these covariates using a regression model, no significant difference was observed between the two groups (odds ratio, 0.956; 95% confidence interval, 0.512-1.786; p=0.888). Conclusion: In agreement with randomized controlled trials in study populations with strict selection criteria, our study determined that subcutaneous progesterone was equally effective as vaginally applied progesterone in daily clinical practice in an unselected patient population.

• 한국지반공학회논문집
• /
• 제34권11호
• /
• pp.71-80
• /
• 2018

본 연구에서는 박스형 개착식 철도 터널의 지진 응답을 유사정적 프레임 해석으로부터 평가하였으며 취약도 곡선을 도출하였다. 지반의 영향을 평가하기 위하여 다양한 이상화된 주상도를 사용하였으며 20개의 계측지진기록을 적용하였다. 기존 연구에서 제시된 탄성 모멘트와 항복 모멘트 비로 정의된 손상지수를 사용하여 Minor, Moderate, Extensive 손상상태에 대한 취약도 곡선을 각각 최대지반가속도의 함수로 적용하였다. 연구 결과, 지반 조건은 취약도에 큰 영향을 미치는 것으로 나타났으며 이를 고려하는 곡선의 개발이 중요한 것으로 나타났다. 개발된 취약도 곡선은 기존의 연구에서 도출된 곡선들과 비교하였다. 기존에 제시된 경험적 취약도 곡선은 지반조건의 영향을 고려할 수 없으며 특히 연약 지반에서는 취약도를 과소예측하는 것으로 나타났다.

• Clinical and Experimental Reproductive Medicine
• /
• 제51권1호
• /
• pp.69-74
• /
• 2024

Objective: The purpose of this study was to identify factors associated with twin pregnancy following day 3 double embryo transfer (DET). Methods: This retrospective cohort study incorporated data from 16,972 day 3 DET cycles. The participants were women aged between 18 and 45 years who underwent in vitro fertilization with intracytoplasmic sperm injection (IVF/ICSI) at My Duc Assisted Reproduction Technique Unit (IVFMD), My Duc Hospital, located in Ho Chi Minh City, Vietnam. Results: Of the 16,972 day 3 DET cycles investigated, 8,812 (51.9%) resulted in pregnancy. Of these, 6,108 cycles led to clinical pregnancy, with 1,543 (25.3% of clinical pregnancies) being twin pregnancies. Factors associated with twin pregnancy included age under 35 years (odds ratio [OR], 1.5; 95% confidence interval [CI], 1.32 to 1.71; p<0.001) and cycles involving the transfer of at least one grade I embryo. Relative to the transfer of two grade III embryos, the risk of twin pregnancy was significantly elevated following the transfer of two grade I embryos (OR, 1.40; 95% CI, 1.16 to 1.69; p<0.001) or a combination of one grade I and one grade II embryo (OR, 1.27; 95% CI, 1.05 to 1.55; p=0.001). Conclusion: By analyzing a large number of IVF/ICSI cycles, we identified several predictors of twin pregnancy. These findings can assist medical professionals in tailoring treatment strategies for couples with infertility.

• Structural Engineering and Mechanics
• /
• 제90권3호
• /
• pp.253-261
• /
• 2024

This research explores a new finite element model for the free vibration analysis of bi-directional functionally graded (BDFG) beams. The model is based on an efficient higher-order shear deformation beam theory that incorporates a trigonometric warping function for both transverse shear deformation and stress to guarantee traction-free boundary conditions without the necessity of shear correction factors. The proposed two-node beam element has three degrees of freedom per node, and the inter-element continuity is retained using both C1 and C0 continuities for kinematics variables. In addition, the mechanical properties of the (BDFG) beam vary gradually and smoothly in both the in-plane and out-of-plane beam's directions according to an exponential power-law distribution. The highly elevated performance of the developed model is shown by comparing it to conceptual frameworks and solution procedures. Detailed numerical investigations are also conducted to examine the impact of boundary conditions, the bi-directional gradient indices, and the slenderness ratio on the free vibration response of BDFG beams. The suggested finite element beam model is an excellent potential tool for the design and the mechanical behavior estimation of BDFG structures.

• Advances in nano research
• /
• 제8권4호
• /
• pp.323-333
• /
• 2020

In recent years, there has been an upsurge for the usage of buckling restrained braces (BRB) rather than ordinary braces, as they have evidently performed better. If the overall brace buckling is ignored, BRBs are proven to have higher energy absorption capacity and flexibility. This article aims to deliberate an economically efficient yet adequate type of all-steel BRB, comprised of the main components as in traditional ones, such as : (1) a steel core that holds all axial forces and (2) a steel restrainer tube that hinders buckling to occurr in the core; there is a more practical detailing in the BRB system due to the elimination of a filling mortar. An investigation has been conducted for the proposed rectangular-tube core BRB and it is hysteric behavioral results have been compared to previous researches conducted on a structure containing a similar plate core profile that has the same cross-sectional area in its core. A loss of strength is known to occur in the BRB when the limiting condition of local buckling is not satisfied, thus causing instability. This typically occurs when the thickness of the restrainer tube's wall is smaller than the cross-sectional area of the core plate or its width. In this study, a parametric investigation for BRBs with different formations has been performed to verify the effect of the design parameters such as different core section profiles, restraining member width to thickness ratio and relative cross-sectional area of the core to restrainer, on buckling load evaluation. The proposed BRB investigation results have also been presented and compared to past BRB researches with a plate profile as the core section, and the advantages and disadvantages of this configuration have been discussed, and it is concluded that BRBs with tubular core section exhibit a better seismic performance than the ones with a plate core profile.

• 한국인터넷방송통신학회논문지
• /
• 제18권2호
• /
• pp.169-176
• /
• 2018

본 논문에서는 센서노드가 전력소모를 줄이기 위하여 주기적으로 휴면상태를 갖는 듀티사이클 기반 무선센서 네트워크를 고려한다. 이러한 네트워크에서는 듀티사이클 간격이 커진다면 전력소모는 감소하지만 종단간 지연시간은 늘어나게 된다. 무선센서네트워크의 많은 애플리케이션은 지연시간에 민감하며 패킷이 센서노드로부터 싱크노드에게 전달되는 데 있어서 지연시간제약 요구사항이 있다. 기존의 대부분의 연구는 종단간 지연시간을 줄이는 것에만 초점을 맞추고 지연시간제약에 대해 고려를 하지 않음으로써 종단간지연시간과 전력소모에 대한 균형을 맞추기 어려웠다. 지연시간제약을 고려하는 연구에서도 노드들간의 시각동기화를 요구하거나 노드들이 특정한 분포를 갖는다고 가정하였다. 기존 연구의 이러한 제약을 극복하기 위하여 본 논문에서는 지연시간제약조건을 충족시키면서 동시에 전력소모를 줄이기 위한 듀티사이클 스케쥴링 알고리즘을 제안한다. 먼저 종단간 지연시간의 확률분포를 추정하고 획득한 분포를 이용하여 지연시간제약조건을 만족하는 최대 듀티사이클 간격을 결정한다. 시뮬레이션 결과에 따르면 제안되는 알고리즘은 주어진 지연시간제약 요구사항을 만족하면서도 낮은 전력소모 성능을 보인다.

• 대한조선학회논문집
• /
• 제60권4호
• /
• pp.222-230
• /
• 2023

In the present work, the scale effect on the Boil-Off Rate (BOR) was investigated based on an analytical method to systematically evaluate the thermal performance of a Liquefied Natural Gas (LNG) Cargo Containment System (CCS). A two-dimensional thermal resistance network model was developed to accurately estimate the heat ingress into the CCS from the outside. The analysis was performed for the KC-1 LNG membrane tank under the IGC and USCG design conditions. The ballast compartment of both the LNG tank and cofferdam was divided into six sections and a thermal resistance network model was made for each section. To check the validity of the developed model, the analysis results were compared with those from existing literature. It was shown that the BOR values under the IGC and USCG design conditions were agreed well with previous numerical results with a maximum error of 1.03% and 0.60%, respectively. A SDR, the scale factor of the LNG CCS was introduced and the BOR, air temperature of the ballast compartment, and the surface temperature of the inner hull were obtained to examine the influence of the SDR on the thermal performance. Finally, a correlation for the BOR was proposed, which could be expressed as a simple formula inversely proportional to the SDR. The proposed correlation could be utilized for predicting the BOR of a full-scale LNG tank based on the BOR measurement data of lab-scale model tanks.