Firm Performance in Vietnam:Evidence from Manufacturing Small and Medium Enterprises

This paper examines the performance of domestic non-state manufacturing small and medium enterprises (SMEs) in Vietnam. Specifically, it evaluates firm level technical efficiency and identifies the determinants of technical efficiency of these SMEs. The paper uses an econometric approach based on a stochastic frontier production function to analyse 5,204 observations of SMEs from three surveys conducted in 2002, 2005 and 2007. The results from the estimations reveal that manufacturing SMEs in Vietnam have relatively high average technical efficiency ranging from 84.2 percent to 92.5 percent. The paper further examines the factors influencing efficiency. It finds that firm age, size, location, ownership, cooperation with a foreign partner, subcontracting, product innovation, competition, and government assistance are significantly related to technical efficiency, albeit with varying degrees and directions. Exporting does not appear to influence technical efficiency. The paper offers some evidence-based policy recommendations to improve the technical efficiency and competitiveness of manufacturing SMEs.manufacturing small and medium enterprises, firm performance, technical efficiency, stochastic frontier production function, Vietnam.

Borel-fixed ideals and reduction number

The aim of this paper is to study the relationship between reduction numbers and Borel-fixed ideals in all characteristics. By definition, Borel-fixed ideals are closed under certain specializations which is similar to the strong stability. We will estimate the number of monomials which can be specialized to a given monomial. As a consequence, we obtain a combinatorial version of the well-known Eakin-Sathaye's theorem which bounds the reduction number in terms of the Hilbert function. Furthermore, we show that the bound of Eakin-Sathaye's theorem is attained by the reduction number of a lex-segment monomial ideal. This result answers a question of Conca in the affirmative. We will also show that the reduction number of the lex-segment ideal is bounded exponentially by the reduction number of the given ideal.Comment: 11 page

Kirszbraun extension on connected finite graph

We prove that the tight function introduced Sheffield and Smart (2012) is a Kirszbraun extension. In the real-valued case we prove that Kirszbraun extension is unique. Moreover, we produce a simple algorithm which calculates efficiently the value of Kirszbraun extension in polynomial time

Data Dissemination in Mobile Phone Sensor Networks

Deploying sensors over large areas is costly in terms of configuration, hardware, and maintenance. Using onboard sensors of today mobile phones can significantly reduce the expenses in monitoring areas and disseminating events or data. Via the available short-range Bluetooth and/or WiFi interfaces, measured data are not only gradually delivered, but also possibly more reliable. In our simulation, existing Delay-Tolerant Network routing algorithms show poor performance on a complex network comprising diverse kinds of sensor nodes, such as, mobile phones, cars, and road side units. New approaches that can perform well on such heterogeneous networks are needed. They also need to support exchanging measurements among sensors for more accurate inference. In the early phase, we set up a heterogeneous architecture composed of different sorts of sensors, and propose an algorithm, Unified routing, for routing and disseminating. A further variant of the scheme is being developed. Early simulation results are consistent with theoretical prediction. After finishing the firs step, Unified routing, the focus of our research will be on distributed data processing. Finally, routing and distributed data processing will be investigated in a testbed in a realistic context

Aerosol depolarization ratio at 1565nm in Finland with Halo Doppler lidar

Atmospheric aerosol particles absorb and scatter solar radiation, directly altering the Earth’s radiation budget. These particles also have a complex role in weather and climate by changing cloud physical properties such as reflectivity by acting as cloud condensation nuclei or ice nuclei. Aerosol particles in the boundary layer are important because they pose a negative impact on air quality and human health. In addition, elevated aerosol from volcanic dust or desert dust present an imminent threat to aviation safety. To improve our understanding of the role of aerosol in influencing climate and the capability to detect volcanic ash, a ground-based network of Halo Doppler lidars at a wavelength of 1565 nm is used to collect data of atmospheric vertical profiles across Finland. By comparing the theoretical values of depolarization ratio of liquid clouds with the observed values, bleed through of each lidar is detected and corrected to improve data quality. The background noise levels of these lidars are also collected to assess their stability and durability. A robust classification algorithm is created to extract aerosol depolarization ratios from the data to calculate overall statistics. This study finds that bleed through is at 0.017 ± 0.0072 for the Uto-32 lidar and 0.0121 ± 0.0071 for the Uto-32XR lidar. By examining the time series of background noise level, these instruments are also found to be stable and durable. The results from the classification algorithm show that it successfully classified aerosol, cloud, and precipitation even on days with high turbulence. Depolarization ratios of aerosol across all the sites are extracted and their means are found to be at 0.055 ± 0.076 in Uto, 0.076 ± 0.090 in Hyytiala, 0.076 ± 0.071 in Vehmasmaki and 0.041 ± 0.089 in Sodankyla. These mean depolarization ratios are found to vary by season and location. They peak during summer, when pollen is abundant, but they remain at the lowest in the winter. As Sodankylä is located in the Artic, it has aerosols with lower depolarization ratio than other sites in most years. This study found that in summer, aerosol depolarization ratio is positively correlated with relative humidity and negatively correlated with height. No conclusion was drawn as to what processes play a more important role in these correlations. This study offers an overview of depolarization ratio for aerosol at a wavelength of 1565 nm, which is not commonly reported in literature. This opens a new possibility of using Doppler lidars for aerosol measurements to support air quality and the safety of aviation. Further research can be done test the capability of depolarization ratio at this wavelength to differentiate elevated aerosol such as dust, pollution, volcanic ash from boundary layer aerosol

Towards Opportunistic Data Dissemination in Mobile Phone Sensor Networks

Recently, there has been a growing interest within the research community in developing opportunistic routing protocols. Many schemes have been proposed; however, they differ greatly in assumptions and in type of network for which they are evaluated. As a result, researchers have an ambiguous understanding of how these schemes compare against each other in their specific applications. To investigate the performance of existing opportunistic routing algorithms in realistic scenarios, we propose a heterogeneous architecture including fixed infrastructure, mobile infrastructure, and mobile nodes. The proposed architecture focuses on how to utilize the available, low cost short-range radios of mobile phones for data gathering and dissemination. We also propose a new realistic mobility model and metrics. Existing opportunistic routing protocols are simulated and evaluated with the proposed heterogeneous architecture, mobility models, and transmission interfaces. Results show that some protocols suffer long time-to-live (TTL), while others suffer short TTL. We show that heterogeneous sensor network architectures need heterogeneous routing algorithms, such as a combination of Epidemic and Spray and Wait