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Search Results: 1 - 10 of 8181 matches for " Khac-Hung Nguyen "
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Thyroid gland cutaneous fistula secondary to a migratory fish bone: a case report
Toyoaki Ohbuchi, Takahisa Tabata, Khac-Hung Nguyen, Jun-ichi Ohkubo, Akiko Katoh, Hideaki Suzuki
Journal of Medical Case Reports , 2012, DOI: 10.1186/1752-1947-6-140
Abstract: A 56-year-old Japanese woman presented with a two-month history of a painless cutaneous fistula in her anterior neck with pus discharge. Endoscopic examinations showed no abnormality, but computed tomography revealed a bone-density needle-shaped foreign body sticking out anteroinferior from the esophagus wall, penetrating through her left thyroid lobe and extending nearly to the anterior cervical skin. A migratory fish bone was suspected, and the foreign body was removed under general anesthetic, combined with a hemithyroidectomy. The injured esophageal mucosa was sutured and closed. Our patient’s postoperative course was uneventful, and she was allowed oral food intake seven days after the surgery. No evidence of recurrence was seen over the postoperative follow-up period of 42?weeks.We should be aware that fish bone foreign bodies may migrate out of the upper digestive tract and lodge in the thyroid gland.
Impacts of Exchange Rate Volatility and FDI on Technical Efficiency—A Case Study of Vietnamese Agricultural Sector  [PDF]
Nguyen Khac Minh, Pham Van Khanh, Nguyen Viet Hung
American Journal of Operations Research (AJOR) , 2015, DOI: 10.4236/ajor.2015.54025
Abstract: The objective of this research is to examine impacts of exchange rate volatility and FDI on efficiency of the Vietnamese agricultural sector at the provincial level for the period 1998-2011. Due to the characteristic of high uncertainty in agricultural production, the chance-constrained programming model would be used to estimate efficiency of the agricultural production sector. In order to study impacts of exchange rate volatility and FDI, we employ the two-stage model. In the first stage, we use the chance-constrained programming model to measure technical efficiency and ARIMA model to quantify exchange rate volatility. In the second stage, we use the fixed effect model to evaluate impacts of exchange rate volatility and FDI on efficiency of agricultural production in poor and rich provinces. The estimated results show that fluctuation in exchange rate volatility would reduce efficiency in agricultural production but FDI has an insignificant impact on the efficient production in Vietnam agricultural sector.
Expanded Barro Regression in Studying Convergence Problem  [PDF]
Nguyen Khac Minh, Nguyen Khac Minh, Pham Van Khanh
American Journal of Operations Research (AJOR) , 2014, DOI: 10.4236/ajor.2014.45029
Abstract: This study develops the approach by Minh & Khanh [1] to the classic Barro and Sala-i-Martin method [2], [3] named “expanded Barro regression method”, and applies this approach in analyzing the convergence of provincial per capita GDP in Vietnam over the period of 1991-2007. Different aspects of provincial convergence are considered in this paper. The estimated result on conver-gence from our model is compared to other models.
A Chance–Constrained Data Envelopment Analysis Approach to Problem Provincial Productivity Growth in Vietnamese Agriculture from 1995 to 2007  [PDF]
Nguyen Khac Minh, Pham Van Khanh
Open Journal of Statistics (OJS) , 2011, DOI: 10.4236/ojs.2011.13026
Abstract: This study employs a chance-constrained data envelopment analysis (CDEA) approach with two models (model A and model B) to decompose provincial productivity growth in Vietnamese agriculture from 1995 to 2007 into technological progress and efficiency change. The differences between the chance - constrained programming model A and model B are assumptions imposed on the covariance matrix. The decomposition allows us to identify the contributions of technical change and the improvement in technical efficiency to productivity growth in Vietnamese production. Sixty-one provinces in Vietnam are classified into Mekong - technology and other -technology categories. We conduct a Mann-Whitney test to verify whether the two samples, the Mekong technology province sample and the other technology sample, are drawn from the same productivity change populations. The result of the Mann-Whitney test indicates that the differences between the Mekong technology category and the other technology category from two models are more significant. Two important questions are whether some provinces in the samples could maintain their relative efficiency rank positions in comparison with the others over the study period and how to further examine the agreements between the two models. The Kruskal - Wallis test statistic shows that technical efficiency from both models for some provinces are higher than those of them in the study period. The Malmquist results show that production frontier has contracted by around 1.3 percent and 0.31 percent from chance-constrained model A and model B, respectively, a year on average over the sample period. To examine the agreements or disagreements in the total factor productivity indexes we compute the correlation between Malmquist indexes, which is positive and not very high. Thus there is a little discrepancy between the two Malmquist indexes, estimated from the chance - constrained models A and B.
Forecasting the Convergence State of per Capital Income in Vietnam  [PDF]
Nguyen Khac Minh, Pham Van Khanh
American Journal of Operations Research (AJOR) , 2013, DOI: 10.4236/ajor.2013.36047
Abstract: Convergence problem of an economic variable represents an underlying forecast of neoclassical economic growth model. This paper aims to analyze the convergence of provincial per capita GDP stability in Vietnam over the period of 1991-2007. This can be done by two approaches including bias data-based regression method for testing convergence and Markov chain model for describing features of long-term tendency of per capita income in Vietnam growth in provinces. The regression method results in the signs of convergence. To apply Markov process, we divide total pattern into 5 per capita income classes. Result estimated from the Markov chain model shows the poor convergence.
The Optimal Stopping Time for Selling an Asset When It Is Uncertain Whether the Price Process Is Increasing or Decreasing When the Horizon Is Infinite  [PDF]
Nguyen Khac Minh, Nguyen Thanh Trung, Pham Van Khanh
American Journal of Operations Research (AJOR) , 2018, DOI: 10.4236/ajor.2018.82007
Abstract: Assume that we want to shell an asset with unknown drift but known that the drift is a two value random variable, and the initial distribution can be estimated. As time goes by, this distribution is updated and base on the probability of the drift takes the small one gives us the stopping rule. Research results show that the optimal strategy to sell the asset is if the initial probability that the drift receives a small value greater than a certain threshold then liquidates the asset immediately, otherwise the asset holder will wait until the probability of the drift receives a small value passing a certain threshold, it is the optimal time to liquidate the asset.
Super Efficiency and Misallocation: Evidence from Vietnamese Electric-Computer Industry  [PDF]
Nguyen Khac Minh, Pham Van Khanh, Nguyen Thi Phuong
American Journal of Operations Research (AJOR) , 2018, DOI: 10.4236/ajor.2018.82006
Abstract: Misallocation means that the source is not distributed efficiently. This leads to an important question of how the relationship between misallocation and efficiency is (see [1]). The purpose of this study is to address the empirical relationship between misallocation and efficiency in the electric and computer industry in Vietnam during the 2005-2015 periods. To do this, we built a model that allowed us to evaluate the impact of misallocation and other factors on efficiency. The slack-based measured efficiency (SBM) model (Tone [2]), and the super-efficient model (Tone [3]) are used to estimate the firms’ efficiency. The approach of Hsieh and Klenow [4] is used to measure misallocation in the study area. Estimated results of the model about the relationship between misallocation and efficiency show that the variable representing the misallocation has a negative sign and statistical significance in all models. In other words, the misallocation negatively affects efficiency. The bigger the misallocation, the lower the efficiency.
A New Approach for Ranking Efficient Units in Data Envelopment Analysis and Application to a Sample of Vietnamese Agricultural Bank Branches  [PDF]
Nguyen Khac Minh, Pham Van Khanh, Pham Anh Tuan
American Journal of Operations Research (AJOR) , 2012, DOI: 10.4236/ajor.2012.21015
Abstract: This paper proposes a new approach for ranking efficiency units in data envelopment analysis as a modification of the super-efficiency models developed by Tone [1]. The new approach based on slacks-based measure of efficiency (SBM) for dealing with objective function used to classify all of the decision-making units allows the ranking of all inefficient DMUs and overcomes the disadvantages of infeasibility. This method also is applied to rank super-efficient scores for the sample of 145 agricultural bank branches in Viet Nam during 2007-2010. We then compare the estimated results from the new SCI model and the exsisting SBM model by using some statistical tests.
Productivity Growth, Technological Progress, and Efficiency Change in Vietnamese Manufacturing Industries: A Stochastic Frontier Approach  [PDF]
Nguyen Khac Minh, Pham Van Khanh, Nguyen Thi Minh, Nguyen Thi Phuong Anh
Open Journal of Statistics (OJS) , 2012, DOI: 10.4236/ojs.2012.22028
Abstract: This study applies a stochastic frontier production approach to decompose the sources of total productivity (TFP) growth into technical progress and changes in technical efficiency of 8057 firms in Vietnamese manufacturing industries during 2003-2007. Using both total manufacturing industry and sub-manufacturing industrial regressions, the analysis focuses on the trend of technological progress (TP) and technical efficiency change (TEC), and the role of productivity change in economic growth. According to the estimated results, the annual technical progress for the manufacturing industry and sub-manufacturing industries are calculated directly from the estimated parameters of the translog stochastic frontier production function by taking a partial derivative of output with respect to time t. The average technical changes in manufacturing industry and sub-manufacturing industries are positive, with an average technical change about 5.2%, 5.8%, 5.4%, 11.8%, 4.6%, 4.1%, 7.3%, 4.8%, 4.8% and 4.8% for total sample, food products & beverages, textile & wearing apparel, footwear, paper & products, industrial chemicals, rubber & plastic products, non- metallic mineral, basic & fabricated metal and other sub-industries, respectively. Total TFP in the manufacturing sector has grown at the annual rate of 0.052, although the rate of growth decreased continuously during the sample period. For the sub-industry estimates during the sample period, TFP grew fastest in the footwear sub-industry, with annual average growth rate of 11.8%, followed by the rubber & plastic products with a rate of 7.3%, and the food products & beverages with a rate of 5.8% per annum.
Determination of ppt Level Chromium(VI) Using the Gold Nano-Flakes Electrodeposited on Platinum Rotating Disk Electrode and Modified with 4-Thiopyridinium  [PDF]
Huy Du Nguyen, T. Thuy Luyen Nguyen, Khac Manh Nguyen, T. Anh Tuyet Tran, Anh Mai Nguyen, Quoc Hien Nguyen
American Journal of Analytical Chemistry (AJAC) , 2015, DOI: 10.4236/ajac.2015.65045
Abstract: The nano-gold layer formed on the platinum rotating disk electrode (nano-Au/Pt-RD) inherited the catalytic property for Cr(VI) reduction from platinum surface and owned the good features of nano-gold such as insensitivity with hydrogen ion, high surface area, augmenting diffusion of Cr(VI) and ability for self-assembling with 4-pyridine-ethanethiol (PET) through Au←S linkages, to form PET/nano-Au/Pt-RD electrode capable of accumulating Cr(VI) from sample. The obtained PET/ nano-Au/Pt-RD electrode showed an extreme sensitivity to Cr(VI). By using this electrode, 1.09 ng·L﹣1 was the detection limit of differential pulse adsorptive cathodic stripping voltammetry for Cr(VI) with the accumulation time of only 2 min. Moreover, this electrode was reproducible with 3.5% RSD for 30 times of Cr(VI) accumulating and stripping. In addition, this electrode was also selective for Cr(VI) determination, which was not almost interfered by other inorganic ions.
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