Byung-Hyun Lee

Thermal sensor allocation and placement for reconfigurable systems

A dynamic monitoring of thermal behavior of hardware resources using thermal sensors is very important to maintain the operation of systems safe and reliable. This article addresses the problem of thermal sensor allocation and placement for reconfigurable systems. For programmable logic arrays, the degree of the use of hardware resources in the systems highly depends on the target application to be implemented, making the allocation of thermal sensors at the manufacturing stage inadequate (or too costly if implemented) due to the unpredictable thermal profile. This means that the thermal sensor allocation could be processed at the time when the reconfigurable logic is implemented (i.e., at the post manufacturing stage). This work proposes an effective solution to the problem of thermal sensor allocation and placement at the post-manufacturing stage. Specifically, we define the Sensor Allocation and Placement Problem (SAPP), and propose a solution which formulates SAPP into the Unate-Covering Problem (UCP) and solves it optimally. Also we combine SAPP with temperature correlation to reduce required sensors more aggressively and propose a solution by applying UCP again. We then provide an extended solution to handle a practical design issue where the hardware resources for the sensor implementation on specific array locations have already been used up by the application logic. Experimental results using MCNC benchmarks show that our proposed technique uses 62.4% and 19.7% less number of sensors to monitor hotspots on the average than that used by the grid-based and the bisection-based approaches while the overhead of auxiliary circuitry is minimized, respectively.

Optimal allocation and placement of thermal sensors for reconfigurable systems and its practical extension

A dynamic monitoring of thermal behavior of hardware resources using thermal sensors is very important to maintain the operation of systems safe and reliable. This work proposes an effective solution to the problem of thermal sensor allocation and placement for reconfigurable systems at the post-manufacturing stage. Specifically, we define the sensor allocation and placement problem (SAPP), and propose a solution which formulates SAPP into the unate-covering problem (UCP) and solves it optimally. We then provide an extended solution to handle a practical design issue where the hardware resources for the sensor implementation on specific array locations have already been used up by the application logic. Experimental results using MCNC benchmarks show that our proposed technique uses 19.7% less number of sensors to monitor hotspots on the average than that used by the bisection based (Mukherjee et al., 2006) approaches.

Separation Control Characteristics of Synthetic Jets with Circular Exit Array

This paper presents experimental and computational investigations on the characteristics of synthetic jets with a circular exit array. Flow characteristics of a piezoelectrically driven synthetic jet with a circular exit array have been investigated under various flow conditions. Step-by-step experiments were conducted to find an improved configuration of a circular exit array while some parameters are kept the same, such as oscillation frequency, input voltage, and exit area. Comparative studies were conducted for a quiescent condition, a forced separated flow, and a separated flow on a high angle of attack. For a quiescent condition, the jet characteristics depending on the total hole perimeter and the oscillation frequency were compared by measuring velocity profiles using a hot-wire anemometry. For a forced separated flow, pressure distributions on an inclined flat plate were examined by changing parameters, such as hole diameter, hole gap, synthetic jet array type, and oscillation phase. Experimental results were analyzed with the help of the computed vortical structures in a quiescent condition and a forced separated flow condition. Based on the comparisons, proper range of design parameters for an improved circular exit array was obtained, and it was observed that the circular exit array based on the design parameters provides a better performance in terms of separation control. For a separated flow over an airfoil at a high angle of attack, the flow control performance of a synthetic jet was verified by measuring aerodynamic coefficients. Based on various comparisons, a synthetic jet with an improved circular exit array was found to be effective for flow separation control.

Callus Induction and Plant Regeneration from Mature Seeds of Timothy

ABSTRACT Timothy ( Phleum pratense L.) is an important grass species as forage. In order to optimize tissue culture conditions of timothy, the effects of plant growth regulators on callus induction and plant regeneration was investigated with mature seeds of colt cultivar. The optimal concentration of 2,4-D for the induction of primary callus from mature seeds was 3 mg/L. The highest embryogenic callus frequency (25%) was observed when the mature seed were cultured on MS medium supplemented with 3 mg/L 2,4-D and 0.1 mg/L BA. The highest plant regeneration frequency was observed when type B callus was transferred to N6 medium supplemented with 1 mg/L 2,4-D and 3 mg/L BA. Regenerated plants were grown normally when shoots were transplanted to the soil. A short tissue culture period and regeneration system would be beneficial for molecular breeding of timothy by the production of transgenic plant.( Key words : Timothy, Callus, Plant regeneration, Tissue culture) Ⅰ. 서 론 티모시( Phleum pratense

Plant Regeneration Capacity of Calluses Derived from Mature Seed of Perennial Ryegrass Cultivars

Ki-WonLee *,** ,JoungKyongLee *,Ki-YongKim *,HeeChungJi*,HyungSooPark*,Kyung-HeeKim ** ,Byung-HyunLee** andSang-HoonLee *ABSTRACTA suitable system for plant regeneration has been established for perennial ryegrass (Loliumperenne L.).In order to investigate the effects of genetic variations of perennial ryegrass in tissue culture response, calliwere induced from mature seeds of five cultivars, ‘Topgun’, ‘Accent’, ‘Renenge GLX’, ‘Tetrellite’, ‘Bison’and plant regeneration frequency was compared. Significant differences were observed among the cultivarsin both callus induction and plant regeneration. Genotype ‘Accent’ consistently performed best in the callusformation and plant regeneration. These results can be used useful for molecular breeding of perennialryegrass through genetic transformation.(Keywords :Callus, Plant regeneration, Cultivar, Molecular breeding, Perennial ryegrass)

Effect of Plant Growth Regulators on Callus Induction and Plant Regeneration of Perennial Ryegrass (Lolium perenne L.)

Optimum tissue culture conditions for an efficient induction of embryogenic callus from mature seeds of perennial ryegrass (Lolium perenne L.) and regeneration of plants from callus tissues were investigated. MS medium containing 3 mg/L 2,4-D and 0.1 mg/L BA was optimal for embryogenic callus induction from mature seeds. The highest plant regeneration frequency (58.3%) was observed when the embryogenic callus tissues were cultured on N6 medium supplemented with 1 mg/L 2,4-D and 3 mg/L BA. Regenerated plants were grown normally when shoots transplanted to the soil. A short tissue culture period and high-frequency regeneration system would be helpful for molecular breeding of perennial ryegrass through Agrobacterium-mediated genetic transformation.

Experimental and Computational Study on Separation Control Performance of Synthetic Jets with Circular Exit

This paper presents experimental and computational investigations of synthetic jets with a circular exit for improving flow control performance. First, the flow feature and vortex structure of a multiple serial circular exit were numerically analyzed from the view point of flow control effect under a cross flow condition. In order to improve separation control performance, experimental and numerical studies were conducted according to several key parameters, such as hole diameter, hole gap, the number of hole, jet array, and phase difference. Experiments were carried out in a quiescent condition and a forced separated flow condition using piezoelectrically driven synthetic jets. Jet characteristics were compared by measuring velocity profiles and pressure distributions. The interaction of synthetic jets with a freestream was examined by analyzing vortical structure characteristics. For separation control performance, separated flow over an airfoil at high angles of attack was employed and the flow control performance of the proposed synthetic jet was verified by measuring aerodynamic coefficient. The circular exit with a suitable hole parameter provides stable and persistent jet vortices that do beneficially affect separation control. This demonstrates the flow control performance of circular exit array could be remarkably improved by applying a set of suitable hole parameters.

Active Flow Control on a UCAV Planform Using Synthetic Jets

This paper deals with experimental investigation of active flow control via synthetic jets using an unmanned combat air vehicle (UCAV) planform. Fourteen arrays of synthetic jets, mounted along both leading edges, were fully or partially activated to increase aerodynamic efficiency and reduce pitch-up moment. The measurements were carried out using a six-component external balance, a pressure scanner, and tuft flow visualization. It was observed that aerodynamic efficiency (L/D) and pitching moment were clearly affected by the location of jets. In particular, inboard and outboard actuation could effectively increase L/D. Moreover, inboard actuation showed a reduction in the pitch-up, even more than that generated by the full actuation. These results suggest that inboard actuation not only effectively increases L/D but also reduces the pitch-up using only a few actuators.

Factors influencing Agrobacterium-mediated transformation efficiency in perennial ryegrass.

A system for the production of transgenic plants has been developed for perennial ryegrass (Lolium perenne L.) via Agrobacterium-mediated transformation. Included in this study were two factors which may affect the gene transfer efficiency: concentrations of acetosyringone (AS, 0 to 300 ), and co-culture period (1 to 7 days). Both factors were very important to achieve high efficiency gene transformation in the perennial ryegrass. The highest transformation efficiency was obtained when embryogenic calli were inoculated with Agrobacterium in the presence of 100 AS with the culture medium for 5 days. Phosphinothricin resistant calli were developed with into complete plants. GUS histochemical assay, polymerase chain reaction (PCR) and Northern blot analysis of transgenic plants demonstrated that transgenes were integrated into the genome of perennial ryegrass. Using this protocol, it was possible to obtain transformants efficiently for further study.

Characterization of Transgenic Tall Fescue Plants Overexpressing NDP Kinase Gene in Response to Cold Stress

Sang-HoonLee *,** ,Ki-WonLee*,** ,KyungHeeKim *,Dae-JinYun *,Sang-SooKwak***andByung-HyunLee *ABSTRACTOxidative stress is the main limiting factor in crop productivity. To solve global environmental problemsusing the plant biotechnology, we have developed on the oxidative stress-tolerant transgenic tall fescueplants via Agrobacterium -mediated genetic transformation method. In order to develop transgenic tall fescue(Festucaarundinacea Schreb.) plants with enhanced tolerance to multiple environmental stresses, nucleotidediphosphate kinase gene under the control of CaMV35S promoter were introduced into genome of tallfescue plants. Proteomic analysis revealed that transgenic tall fescue not only accumulated NDP kinase 2protein in their cells, but also induced several other antioxindative enzyme-related proteins. When leaf discsof transgenic plants were subjected to cold stress, they showed approximately 30% less damage thanwild-type plants. In addition, transgenic tall fescue plants showed normal growth when transgenic plantswere subjected to 4 for 3 days treatments. These results suggest that transgene is important in ROSscavenging by induction of antioxidative proteins, and could improve abiotic stress tolerance in transgenictall fescue plants.(Keywords :Tall fescue, Antioxidant gene, Agrobacterium , Transformation)