Cross-Layer Performance Analysis of CSMA/iCA Based Wireless Local Area Network

Carrier sense multiple access with improvised collision avoidance (CSMA/iCA) has recently been proposed as an enhancement to CSMA/CA. It has been reported to be superior than the legacy counterpart in terms of throughput efficiency, packet transmission delay and quantitative fairness index. Nevertheless, the superiority has been shown assuming ideal network conditions: error-free physical layer (L1) and saturated (always non empty) queue at medium access control layer (L2). These strict assumptions, however, do not accurately hold in the real-world Wireless Local Area Networks since the wireless medium is generally error-prone and the arrival of the packets at L2 queue is generally bursty resulting in non-saturated queue occupancy. Thus, the reported performance, especially throughput, in such typical L1/L2 settings is not complete to understand the performance benefit that CSMA/iCA offers under the realistic network settings. In this paper, we relax the aforesaid ideal assumptions and present a cross-layer (L1/L2) performance analysis. Our cross-layer analytical model considers the effect of Rayleigh fading induced bit errors in L1 and non-saturated queue occupancy due to Poisson packet arrival at L2 queue. By virtue of the validated numerical results, we show that the CSMA/iCA consistently retains its throughput gain over CSMA/CA for the non-ideal wireless settings as well.     

A novel Adaptive Cluster Transformation (ACT)-based intrusion tolerant architecture for hybrid information technology

Recently, the building of strong intrusion tolerant systems is in great demand since the openness and the distributed nature of information systems are easily used to compromise the systems by intentional attacks. To achieve intrusion tolerance by enabling the systems to survive various types of intrusions, we suggest a novel approach, Adaptive Cluster Transformation (ACT), in this paper. Instead of using a fixed cluster size as in conventional approaches, ACT adapts a variable cluster size depending on the system status. This is proved to maintain good quality of service (QoS). In addition, the early prediction of incoming massive packets makes ACT possible to replace any damaged clusters with new ones consisting of pristine virtual machines (VMs). This also contributes to defend the system against a Denial of Service (DoS). The performance of ACT is compared with other fixed sizes of VM cluster architectures by CSIM 20. And it is verified that the proposed method is more effective in maintaining the specific level of QoS as well as providing strong security to the targeted system.     

Developmental and Neurotoxicity of Acrylamide to Zebrafish

Acrylamide is a commonly used industrial chemical that is known to be neurotoxic to mammals. However, its developmental toxicity is rarely assessed in mammalian models because of the cost and complexity involved. We used zebrafish to assess the neurotoxicity, developmental and behavioral toxicity of acrylamide. At 6 h post fertilization, zebrafish embryos were exposed to four concentrations of acrylamide (10, 30, 100, or 300 mg/L) in a medium for 114 h. Acrylamide caused developmental toxicity characterized by yolk retention, scoliosis, swim bladder deficiency, and curvature of the body. Acrylamide also impaired locomotor activity, which was measured as swimming speed and distance traveled. In addition, treatment with 100 mg/L acrylamide shortened the width of the brain and spinal cord, indicating neuronal toxicity. In summary, acrylamide induces developmental toxicity and neurotoxicity in zebrafish. This can be used to study acrylamide neurotoxicity in a rapid and cost-efficient manner.     

Carrier sense multiple access with improvised collision avoidance and short-term fairness

In this paper, we present a simple method to simultaneously enhance collision avoidance efficiency and short-term fairness of a most popular contention based medium access control protocol, carrier sense multiple access with collision avoidance. The key idea here is to adaptively tune the shape of contention slot selection distribution over the temporal contention window during ongoing collision resolution process which, in the legacy scheme, used to be flat throughout. The tuning mechanism is such designed that it not only maximizes the selection likelihood of relatively less collision prone contention slots over the contention window but also compensates the idle delay that the contending stations have suffered in their recent access attempt. Through rigorous numerical and simulation based analysis, the proposed scheme is shown to enhance the performance of a IEEE 802.11 based distributed wireless network in terms of network throughput efficiency and packet transmission delay while allowing individual stations to share the channel fairly even in short time scale.     

Packet Loss Fair Scheduling Scheme for Real‐Time Traffic in OFDMA Systems

In this paper, we propose a packet scheduling discipline called packet loss fair scheduling, in which the packet loss of each user from different real‐time traffic is fairly distributed according to the quality of service requirements. We consider an orthogonal frequency division multiple access (OFDMA) system. The basic frame structure of the system is for the downlink in a cellular packet network, where the time axis is divided into a finite number of slots within a frame, and the frequency axis is segmented into subchannels that consist of multiple subcarriers. In addition, to compensate for fast and slow channel variation, we employ a link adaptation technique such as adaptive modulation and coding. From the simulation results, our proposed packet scheduling scheme can support QoS differentiations while guaranteeing short‐term fairness as well as long‐term fairness for various real‐time traffic.     

Time dynamics of overlapping e-auction mechanisms: Information transfer, strategic user behavior and auction revenue

This paper investigates the time dynamics of user strategic patterns and resulting welfares in a series of overlapping multiple online auctions. An auction mechanism is a dynamic game where the valuation and strategic space of bidders determine the outcomes. When those mechanisms exist concurrently or in a series in a market environment, multiple sources are visible and accessible, such that there is likely to be a form of interdependency across the auctions. While heterogeneous bidder behavior has been studied in some literature, the focus is mainly on an individual auction level and the underlying dynamics regarding the interdependency across the auctions in the market has not been explained. We use a two-phased approach to address this discrepancy. First, we classify user strategy using k-means clustering. Then, we characterize the transition pattern of heterogeneous clusters using a dynamic systems framework. Long-term behavior of the system is effectively and efficiently predicted using system parameters. The empirically calibrated simulation, which supports the analytical properties, provides managerial insights in designing multiple overlapping online auction market.     

ML Approaching MIMO Detection Based on Orthogonal Projection

A detection algorithm for spatially multiplexed multiple input multiple output (MIMO) systems is proposed. The receiver first estimates the MIMO channel and rearranges the layers according to the measured SNRs. To determine the candidate vectors, an orthogonal projection combined with the M-algorithm is used. Without performing the exhaustive full search of the maximum likelihood (ML) method, the proposed algorithm can reach the performance which is closely akin to the ML method. The computational complexity markedly decreases: 0.66% over the ML method in terms of the number of real multiplications.     

Battery-Free,Wireless, Ionic Liquid Sensor Arrays to Monitor Pressure and Temperature of Patients in Bed and Wheelchair

Repositioning is a common guideline for the prevention of pressure injuries of bedridden or wheelchair patients. However, frequent repositioning could deteriorate the quality of patient's life and induce secondary injuries. This paper introduces a method for continuous multi-site monitoring of pressure and temperature distribution from strategically deployed sensor arrays at skin interfaces via battery-free, wireless ionic liquid pressure sensors. The wirelessly delivered power enables stable operation of the ionic liquid pressure sensor, which shows enhanced sensitivity, negligible hysteresis, high linearity and cyclic stability over relevant pressure range. The experimental investigations of the wireless devices, verified by numerical simulation of the key responses, support capabilities for real-time, continuous, long-term monitoring of the pressure and temperature distribution from multiple sensor arrays. Clinical trials on two hemiplegic patients confined on bed or wheelchair integrated with the system demonstrate the feasibility of sensor arrays for a decrease in pressure and temperature distribution under minimal repositioning.     

Experimental study on the icing characteristics of LPLi injectors under various injection conditions

Development of alternative fuels has been increasing to replace conventional fuels because of severe environmental pollution from the exhaust emissions of ground vehicles and the depletion of fossil fuels. LPG (Liquefied petroleum gas) fuel provides clean energy for gasoline-fueled engines and LPG fuel R&D (Research & development) has actively progressed in reaching the application stage. However, the icing phenomenon in liquid-phase LPG injection systems remains a major problem. The purpose of this study was therefore to investigate the temperature distribution on the icing protection tip and icing formation characteristics under various test conditions (i.e. injection pressure, injection frequency, injection duty). The results showed that increasing the injection frequency induced a big the temperature drop, whereas increasing the injection duty decreased the temperature drop under the same test conditions. Increasing the injection pressure caused a small temperature drop because of an increase in the injection velocity, which meant that much of the injected LPG evaporated at a region distant from the nozzle tip. The protection tip with a double-hollow structure had a smaller the temperature drop than the all-in-one type protection tip made of the same material (copper).

     

Investigation of Ifosfamide Toxicity Induces Common Upstream Regulator in Liver and Kidney

Ifosfamide is an alkylating agent, a synthetic analogue of cyclophosphamide, used to treat various solid cancers. In this study, the toxicity of ifosfamide was evaluated using single-and multiple-dose intraperitoneal administration in rats under Good Laboratory Practice guidelines, and an additional microarray experiment was followed to support toxicological findings. A single dose of ifosfamide (50 mg/kg) did not induce any pathological changes. Meanwhile, severe renal toxicity was observed in the 7 and 28 days consecutively administered groups, with significant increases in blood urea nitrogen and creatinine levels. In the tox-list analysis, cholesterol synthesis-related genes were mostly affected in the liver and renal failure-related genes were affected in the kidney after ifosfamide administration. Moreover, interferon regulatory factor 7 was selected as the main upstream regulator that changed in both the liver and kidney, and was found to interact with other target genes, such as ubiquitin specific peptidase 18, radical S-adenosyl methionine domain containing 2, and interferon-stimulated gene 15, which was further confirmed by real-time RT-PCR analysis. In conclusion, we confirmed kidney-biased ifosfamide organ toxicity and identified identically altered genes in both the liver and kidney. Further comprehensive toxicogenomic studies are required to reveal the exact relationship between ifosfamide-induced genes and organ toxicity.