Seung-Kyu Park

Real-time scheduling of tasks that contain the external blocking intervals

Distributed systems, where the processes send and receive their messages remotely, are generally based on the message communications. The execution of a process is blocked until the process receives a response from an other process for a requested message. In this paper, we propose two real-time scheduling methods for the tasks with blocking intervals. It is proven that every task set that is schedulable by Mings method is also schedulable by one of the proposed methods. Also, the simulation shows that the schedulable ratios of task sets by the proposed methods are much higher than that obtained by Mings method.

Cytopathic changes and pro-inflammatory cytokines induced by Naegleria fowleri trophozoites in rat microglial cells and protective effects of an anti-Nfa1 antibody

Naegleria fowleri, a free‐living amoeba, causes fatal primary amoebic meningoencephalitis in experimental animals and humans. The nfa1 gene (360 bp) was previously cloned from a cDNA library of pathogenic N. fowleri by immunoscreening, and produced a 13·1‐kDa recombinant protein that showed pseudopodia‐specific localization by immunocytochemistry. On the basis of an idea that the pseudopodia‐specific Nfa1 protein seems to be involved in the pathogenicity of N. fowleri, the cytopathic activity of N. fowleri trophozoites co‐cultured with rat microglial cells was observed, and the effects of an anti‐Nfa1 antibody in a co‐culture system were elucidated. Using light, scanning and transmission electron microscopy, it was seen that N. fowleri trophozoites in contact with microglial cells produced vigorous pseudopodia and a food‐cup structure. Microglial cells were destroyed by N. fowleri trophozoites as seen from necrotic cell death in a time‐dependent manner. In a51Cr release assay, N. fowleri showed 17·8%, 24·9%, 54·6% and 98% cytotoxicity against microglial cells at 3, 6, 12 and 24 h post‐incubation, respectively. However, when anti‐Nfa1 antibody was added in a coculture system, N. fowleri cytotoxicity was reduced to 15·5%, 20·3%, 46·7% and 66·9%, respectively. Moreover, microglial cells co‐cultured with N. fowleri trophozoites secreted the pro‐inflammatory cytokines, TNF‐α, IL‐1β and IL‐6. In the presence of anti‐Nfa1 antibody, the secretion of TNF‐α was slightly, but not significantly, decreased.

Adaptive multimedia stream presentation in mobile computing environment

We present a mechanism of multimedia synchronization for smooth play back of streams in a mobile environment. This mechanism contains an effective buffering method and playout control not only to provide seamless playback of a media stream, but also to minimize the effect of wireless network characteristics. To implement this in a mobile computing environment, we adopted a proxy concept for separating wireless and wired networks. This proxy puts the streams into the buffers from a server and sends them to mobile hosts. It does QoS negotiation with user applications if the network cannot support the required QoS. The proposed buffering method keeps the continuous play of a media stream using a feedback mechanism and playout control provides more natural multimedia presentation by adjusting the frame duration on-screen. Experimental results show that our synchronization scheme provides a constant playback rate even in the frequent short time disconnection and some buffering control parameters affect playback performance by some degree.

A study on a fast measuring technique of wavefront using a Shack-Hartmann sensor

Abstract The measuring resolution and speed for wavefront are important to improve the performance of an adaptive optics system. In this paper, we propose a fast measuring technique with high resolution in the Shack–Hartmann wavefront sensor. The proposed measuring technique of wavefront combines the conventional center of mass algorithm with an estimated weighting factor. The estimated weighting factor is a real value anticipating the real center of mass in a wavefront spot image. This estimated weighting factor can be calculated at the initialization step of an adaptive optics system. We designed a robust adaptive optics system with this proposed measuring algorithm. The measuring accuracy and speed are investigated by using the proposed algorithm compared with the conventional center of mass algorithm in experiments.

Prophylactic Antiemetic Efficacy of Granisetron or Ramosetron in Patients Undergoing Thyroidectomy

OBJECTIVE Thyroidectomy is associated with a high incidence of postoperative nausea and vomiting (PONV), ranging from 60% to 84%. We conducted this study to compare the antiemetic effects and safety of granisetron 20 micro g/kg and ramosetron 4 micro g/kg in patients undergoing elective thyroidectomy under standard anaesthetic technique. METHODS One hundred and thirteen patients were randomized to receive placebo (n = 41), granisetron 20 nug/kg (n = 36) or ramosetron 4 micro g/kg (n = 36) intravenously over 2-5 minutes immediately before the induction of anaesthesia. The incidence of PONV, nausea severity score (NSS), adverse events and the need for rescue antiemetics were assessed during the first 1 hour (0-1 h) and following 23 hours (1-24 h) after anaesthesia. RESULTS During the first hour after anaesthesia, the incidence of PONV was 36.6% for placebo, 11.1% for granisetron (p = 0.012 vs placebo) and 25.0% for ramosetron. During 1 hour to 23 hours after anaesthesia, the incidence of PONV was 51.2% for placebo, 30.6% for granisetron and 41.7% for ramosetron. There were no significant differences between the three groups. Overall (0-24 h), the corresponding incidence of PONV were 61.0%, 30.6% and 50.0%, respectively, showing a significantly lower value in the granisetron group than in the placebo group (p = 0.008). The incidence of vomiting and rescue antiemetic requirement during the first 24 hours after anaesthesia was significantly lower with the granisetron group than with placebo (p = 0.021 and 0.030, respectively). The most common adverse events in the three groups were headache and dizziness. CONCLUSION Only granisetron 20 micro g/kg was superior to placebo for the prevention of PONV after thyroidectomy.

Two-channel spatial phase shifting electronic speckle pattern interferometer

A two-channel spatial phase shifting (SPS) electronic speckle pattern interferometer for the deformation measurement of a transient process was developed. The system was composed of two cameras for the simultaneous acquisition of two phase shifted speckle fringe patterns, and several polarization components for SPS. The phase shifted speckle fringe patterns, captured by two cameras, were analyzed by two kinds of phase change calculation algorithms. Applications of the system to measurement of the object deformation and the analysis of the fringe patterns are described.

AHSEN: autonomic healing-based self management engine for network management in hybrid networks

In this paper, we present a novel self-healing engine for autonomic network management. A light weight Self Management Frame (SMF) performs monitoring and optimization functions autonomously and the other self management functions, driven by context, are invoked on demand from the server. The policies are maintained to calculate the trust factor for network entities and those trust factors will be used at the later stages of our project to enforce resource utilization policies. The plug-ins, residing at the server, are used to perform the on-demand management functions not performed by SMF at client side. A Simple Network Management Protocol (SNMP) based monitoring agent is applied that also triggers the local management entities and passes the exceptions to the server which determines the appropriate plug-in. Considering the amount of resources being put into current day management functions and contemporary autonomic management architectures our findings show improvement in certain areas that can go a long way to improve the network performance and resilience.

A novel autonomic rapid application composition scheme for ubiquitous systems

In this paper we present an autonomic rapid application composition scheme for ubiquitous systems. The main contribution of this paper is to provide a mode through which a mobile user can receive transparent service environment during his mobility period using the benefits of service composition paradigms. We propose a novel service selection matrix that enables the selection of the services similar to the ones that user was previously using. We observed that the user context is not the only key to improve the service selection rather some selection heuristics are also needed. Those search heuristics are provided through the degree of adaptive similarity. Our over all objective is to achieve high levels of service consistency and quality of service at higher layers.

Process monitoring of laser welding using chromatic filtering of thermal radiation

An innovative real-time weld monitoring technique using chromatic filtering of the thermal radiation from a weld pool is developed. The thermal radiation from the weld pool is focused onto an aperture and the transmitted thermal radiation is monitored at two wavelengths with high-speed single-element detectors. Owing to the chromatic aberration introduced in the focusing optics, the transmittance curve of thermal radiation varies according to the wavelength. Owing to this difference in the transmittance, the local variation of thermal radiation from the weld pool can be monitored by recording the two spectral signals from the two detectors. In this paper, the algorithms used to monitor the laser power on the weld specimen and the focus shift of the focusing optics are investigated and the performance of laser power and focus monitoring for pulsed Nd:YAG laser welding is shown.

Priority inversion handling in microkernel-based Real-Time Mike

We propose a resource management model to avoid priority inversion problem that may occur when two tasks attempt to send service requests to a server task, and then the server task sends a request to another server task in a nested fashion. In this model we introduce two new concepts: job identifier inheritance and priority ceiling inheritance. We also suggest a new resource locking condition of the priority ceiling protocol for the computational model of the microkernel-based real-time system, called Mike, in which both IPC and synchronization are utilized and client/server communication model is frequently used in a nested fashion. To see the effectiveness, the proposed model has been implemented in Real-Time Mike developed previously. The implemented system shows that the resource management model efficiently prevents the priority inversion problem and avoids deadlock and multiple blocking.