Search

In Wireless Rechargeable Sensor Networks (WRSNs), charging scheme optimization is one of the most critical issues, which plays an essential role in deciding the sensors’ lifetime. An effective charging scheme should simultaneously consider both the charging path and the charging time. Existing works, however, mainly focus on determining the optimal charging path and adopt the full charging strategy. The full charging approach may increase the sensors’ charging delay and eventually lead to sensor energy depletion. This paper studies how to optimize the charging path and the charging time at the same time to avoid energy depletion in WRSNs. We first formulate the investigated problem with a Mixed-Integer Linear Programming model. We then leverage the bi-level optimization approach and represent the targeted problem with two levels: the charging path optimization at the upper level and the charging time optimization at the lower level. A combination of Genetic Algorithm and Greedy method is proposed to determine the optimal charging path. Besides, to reduce the computational complexity of charging time identification level, we propose a Particle Swarm Optimization (PSO) algorithm to optimize the charging time of the best charging path in each evolutionary generation. The experimental validation on various network scenarios demonstrates our proposed charging scheme’s superiority over the existing algorithms.

With the breakthrough of electromagnetic power transfer technology, wireless charging has emerged as a hopeful solution for the energy provisioning problem in wireless sensor networks. One of the prominent issues that affect the potential exploitation of this technology is the charging scheduling problem. However, existing works on this topic either focus mainly on using a single mobile charger for the whole network or suffer from several common limitations such as enforcing the chargers to visit all sensors or applying the rigid full-charging scheme. Moreover, they rarely delve into maximizing the survival nodes ratio, which impacts directly on the multi-hop communication of the network. This paper addresses the charging scheduling for multiple mobile chargers without the above limitations. We first formulate a maximum survival ratio problem and prove its NP-hardness. A charging scheme that exploits the advantages of the multifactorial evolutionary algorithm is then proposed to optimize the charging paths of all chargers simultaneously. We finally evaluate the efficacy of the proposed algorithm through extensive simulations. The experimental results demonstrate that our scheduling scheme provides promising outcomes in terms of survival ratio and the traveling energy of chargers.

Wireless Rechargeable Sensor Network has emerged as a potential solution for the constrained energy problem in sensor networks in recent years. The charging process has been employed to prolong the sensor’s lifetime. An effective charging algorithm requires simultaneously optimize the charging path and charging time at each charging location under the Mobile Charger’s limited energy. The existing methods, however, are generally lacking in the literature. Moreover, most works are based on the assumption that Mobile Charger has sufficient or infinite energy to visit and charge all sensors within each charging cycle. This constraint leads to prolonging the waiting charging time of energy-hurry sensors and unnecessary visiting of energy-sufficient sensors. In this paper, we aim at minimizing energy depletion and the charging cost of Mobile Charger in Wireless Rechargeable Sensor Networks without the mentioned limitations above. We first mathematically formulate the investigated problem as mixed integer and linear programming. We propose a novel partial charging scheme based on fuzzy logic and genetic algorithms to determine which sensors should be charged in each cycle and optimize both charging paths and charging time simultaneously. A range of experimental simulations is conducted to demonstrate the effectiveness of our charging scheme. The simulation results show our proposed algorithm’s effectiveness compared to the existing works concerning various performance metrics.

In recent years, Wireless Rechargeable Sensor Networks, which exploit wireless energy transfer technologies to address the energy constraint problem in traditional Wireless Sensor Networks, has emerged as a promising solution. There are two important factors that affect the performance of a charging process: charging path and charging time. In the literature, many studies have been done to propose efficient charging algorithms. However, most of the existing works focus only on optimizing the charging path. In this paper, we are the first one to jointly take into account both the charging path and charging time. Specifically, we aim at determining the optimal charging path and the charging time at each charging location to minimize the number of dead nodes. We first mathematically formulate the problem under mixed integer and linear programming. Then, we propose a periodic charging scheme, which is based on the Greedy and Genetic algorithm approaches. The experiment results show that our proposed the algorithm reduces significantly the number of dead nodes compared to a relevant benchmark.

Thanks to the advancements in wireless power transfer technologies, a new paradigm of wireless sensor network (WSNs) called wireless rechargeable sensor networks (WRSNs) has recently emerged. For a WRSN, designing an efficient charging schedule is a challenging issue due to the inherent constraints of WSNs. Although there have been many efforts to optimize the charging schedule, the existing works suffer from several critical problems. Firstly, they rarely tackle the dead node minimization problem, which is the ultimate objective of wireless charging. Secondly, most of the existing works assume impractical conditions, which include the unlimited battery capacity of the charger, and a fully charging scheme at the sensors. In this paper, aiming at minimizing the number of dead nodes, we propose a novel charging scheme based on the genetic algorithm. Our scheme works when the mobile charger has only limited capacity, and the sensors are charged partially at each charging round. The experiment results show that our proposed algorithm reduces the number of dead nodes significantly compared to other existing studies.

Vietnam agricultural cooperatives have a long history of establishment and development from the 1950s. This business model has experienced many stages of rises and falls. The Van Duc Co-operative, operating currently under the condition of the new Cooperative Law of 2012 and specializing in vegetable production and supplying input and output services to its members, is a case of success. Despite challenges of competition and business capital, the success of Van Duc Co-operative is the result of many factors, namely the experience and awareness of famers in safe vegetable production, production strategies and process management, active managers and effective marketing strategies, and external supports. The Van Duc Co-operative benefits local people and the community in many ways; the local people are proud of the cooperative’s brand on safe vegetables, farmers’ minds are changing toward safe products production, and economics and the environment are improved.

Context Chronic noncommunicable diseases (NCDs) have been shown to be major causes of morbidity and mortality in hospitals for the whole country. Objective This study aims to describe the situation of health service utilization among people with NCDs in a rural area and identify association between the situation of health service utilization among people with chronic diseases and their socioeconomic status. Design This was a cross-sectional study. Setting A rural district located in the North of Vietnam. Participants People 15 years of age and older. Health service utilization was analyzed only among people who reported having NCD. Main outcome measures Data were collected through a personal household interview conducted by 12 trained field workers. The dependent variable is health care service utilization among people with chronic NCDs. The explanatory variables include both household attributes such as household economic conditions, and so forth, and individual characteristics. Results Eighteen percent of the adults and 51% of the elderly respondents reported having at least 1 of the NCDs. The proportions of people with NCDs who used at least 1 outpatient service and used at least 1 inpatient health service during the last 12 months were 68.1% and 10.7%, respectively (the nonutilization rates of 31.9% and 89.3%, respectively). The statistically significant correlates of health care service utilization among people with NCDs were ethnicity (ethnic minority was significantly associated with a lower odds of health care service utilization) and health insurance (no health insurance was significantly associated with lower odds of health care service utilization). Conclusion Given the evidence from this study, actions to improve access to health care services among people with NCDs are clearly needed. The capacity of primary health care system for the prevention and control of NCDs should be ranked a top priority.

본고는 2007년 최초 설립 이래 지속적으로 확대되고 있는 한국어 국외 보급 전문기관인 ‘세종학당’에 관심을 두고, 성공적인 운영 기관의 한 사례로 베트남 지역의 하노이2 세종학당을 중심으로 고찰한 논의이다. 먼저 2장에서는 세종학당 관련 기존 성과를 전반적으로 검토한 데 이어 베트남 지역의 한국어 교육과 세종학당에 대한 선행 연구를 개관하였다. 3장에서는 본고의 연구 대상인 하노이2 세종학당의 개요 및 운영 현황을 파악하고 이를 토대로 4장에서는 향후 발전 방안에 대한 시사점을 논하였다. 개별 세종학당들의 성공적인 운영 사례를 발굴하고 면밀히 파악하는 작업은 세계 곳곳 세종학당의 내적 기반을 공고히 하고 현지 실정에 최적화된 세종학당의 모습을 모색하는 데 기초 자료로 삼을 수 있다는 측면에서 본고의 의의가 있다.

Background : In Vietnam, women are at risk of HIV infection due to many factors. However, there is limited evidence about what women know and how they behave to protect themselves from HIV. Objective : The objective of this study was to investigate the trends in comprehensive HIV/AIDS knowledge, attitude, and associated factors among Vietnamese women from 2000 to 2011. Design : Data from three waves of the Vietnam Multiple Indicator Cluster Surveys (years 2000, 2006, and 2011) were used. Logistic regression methods examined factors associated with each of two dependent variables, HIV/AIDS knowledge and attitude toward HIV/AIDS. Results : Although there was an increasing trend in basic HIV/AIDS knowledge and positive attitude toward the disease, in Vietnamese women in the general population over the survey years, the prevalence of women with basic HIV/AIDS knowledge and positive attitude toward HIV/AIDS was low. Multivariable models indicated that women who had higher levels of education, lived in urban areas, had higher economic status, and knew about places of HIV-related services were more likely to have good HIV/AIDS knowledge (e.g. in 2011, AOR’s=3.01; 1.27; 1.88; 2.03, respectively). Women with higher educational attainment, knew about HIV services, and had better HIV knowledge were more likely to report positive attitude toward HIV/AIDS (e.g. in 2011, AOR’s=2.50; 1.72; 2.23, respectively). Conclusions : This study recommends that public health programs for the control of HIV, such as behavioral change communication campaigns or social policies for women, should focus not only in improving the quality of existing HIV/AIDS counseling and testing services but also on expanding coverage to increase accessibility to these services for women in rural areas. In addition, efforts to raise the level of knowledge about HIV/AIDS and improve attitude toward the disease should be undertaken simultaneously. The results of this study can help inform HIV control policies and practices in other developing countries. Keywords: HIV/AIDS knowledge; HIV/AIDS attitude; MICS; Vietnamese women; Vietnam (Published: 29 February 2016) Citation: Glob Health Action 2016, 9 : 29247 - http://dx.doi.org/10.3402/gha.v9.29247 This paper is part of the Special Issue: Millennium Development Goals in Vietnam: the Progress and Social Determinants . More papers from this issue can be found at www.globalhealthaction.net

Background: Knowledge of the aggregate effects of multiple socioeconomic vulnerabilities is important for shedding light on the determinants of growing health inequalities and inequities in maternal healthcare.Objective: This paper describes patterns of inequity in maternal healthcare utilization and analyzes associations between inequity and multiple socioeconomic vulnerabilities among women in Vietnam.Design: This is a repeated cross-sectional study using data from the Vietnam Multiple Indicator Cluster Surveys 2000, 2006, and 2011. Two maternal healthcare indicators were selected: (1) skilled antenatal care and (2) skilled delivery care. Four types of socioeconomic vulnerabilities – low education, ethnic minority, poverty, and rural location – were assessed both as separate explanatory variables and as composite indicators (combinations of three and four vulnerabilities). Pairwise comparisons and adjusted odds ratios were used to assess socioeconomic inequities in maternal healthcare.Results: In all three surveys, there were increases across the survey years in both the proportions of women who received antenatal care by skilled staff (68.6% in 2000, 90.8% in 2006, and 93.7% in 2011) and the proportions of women who gave birth with assistance from skilled staff (69.9% in 2000, 87.7% in 2006, and 92.9% in 2011). The receipt of antenatal care by skilled staff and birth assistance from skilled health personnel were less common among vulnerable women, especially those with multiple vulnerabilities.Conclusions: Even though Vietnam has improved its coverage of maternal healthcare on average, policies should target maternal healthcare utilization among women with multiple socioeconomic vulnerabilities. Both multisectoral social policies and health policies are needed to tackle multiple vulnerabilities more effectively by identifying those who are poor, less educated, live in rural areas, and belong to ethnic minority groups.Keywords: healthcare; skilled antenatal care; skilled delivery; multiple socioeconomic vulnerabilities; inequity; inequality(Published: 29 February 2016)Citation: Glob Health Action 2016, 9: 29386 - http://dx.doi.org/10.3402/gha.v9.29386This paper is part of the Special Issue: Millennium Development Goals in Vietnam: the Progress and Social Determinants. More papers from this issue can be found at www.globalhealthaction.net

A cohort of Japanese encephalitis (JE) survivors in Cambodia and Viet Nam were assessed at least 4 months after hospital discharge in order to understand the extent of disability after JE. We used a simple assessment tool which focuses on the impact on daily life. In total, 64 disability assessments were conducted: 38 in Cambodia and 26 in Viet Nam. In Cambodia, 4 (11%) children had severe sequelae, suggesting the children would likely be dependent, 15 (39%) had moderate sequelae and 17 (45%) had mild sequelae. In Viet Nam, two (8%) persons had severe sequelae, five (19%) had moderate sequelae and eight (31%) had mild sequelae. In many JE-endemic areas there are no multi-disciplinary teams with sophisticated equipment to assess patients after JE disease. This assessment tool can assist with patient management and generate data to support the need for programmes to prevent disease and improve outcomes for survivors.

We have enhanced the WG mode resonator method by using the substrates with the same thickness to evaluate the conductivity and the complex permittivity in the same frequency band. Using the proposed technique we investigate frequency dependencies of PTFE substrate with three types of copper-foils in 55 to 70 GHz band. In the conventional measurements, the conductivity of electrodeposited copper foils is 56% of the value of the international standard annealed copper. However when we used substrates with the same thickness for the measurement the conductivity of electrodeposited copper foil is 35%.

This paper presents a measurement method for conductivity of sandwich-type dielectric substrates in millimeter wave region. In this method, the conductivity is evaluated from the measured resonant characteristics of Whispering Gallery modes in a circular disk sample. The method has an advantage for millimeter wave measurement in terms of the size of resonators with the diameter is about 20~40 times of wavelength. The WG mode resonances can be arisen periodically in order of the mode number in a wide frequency band. We present the measured conductivity of the sandwich-type dielectric substrates with three types of copper foils and compare with the results of copper-clad dielectric substrates in 50- 65 GHz band. The result of conductivity of electrodeposited copper foil is 53% to 60% of conductivity of pure copper and the results of rolled copper foils and both side shinning copper foils is 63% to 71%. These results are almost equal to the results obtained by the use of copper-clad resonator.