Variable Capacity Research Articles

13 - MITOCHONDRIAL DNA HAPLOGROUPS ARE ASSOCIATED WITH PSYCHIATRIC DISEASE: A NATION-WIDE STUDY OF 74,763 DANES

Background Disturbed mitochondrial function has been implicated in psychiatric disease. All mitochondria contain a small maternally inherited DNA (mtDNA) of 16.6 kb. Through evolution and genetic drift, the mtDNA sequence has become fixed into haplogroups (hgs) with a characteristic population and geographical distribution. Different hgs exhibit variable functional capacity and have been demonstrated to be susceptibility factors for various, predominantly degenerative, diseases. Associations with Parkinsons and Alzheimers diseases, as well as cardiac, metabolic and psychiatric disorders have been reported. These findings have prompted the suggestion that variations in mitochondrial function might be susceptibility factors for disease. However, reports on association between mtDNA hgs and disease have frequently been conflicting. This is partly due to population stratification in examined populations and low-powered study designs. We analysed the association between mtDNA hgs and psychiatric disease using a very large geographically unbiased cohort, iPSYCH, comprising 2% of Danes as controls and 50,000+ psychiatric patients. Methods Using DNA extracted from dried blood spots from 50,567 Danish psychiatric patients (ADHD: 13,103; ASD: 12,891; Anorexia: 2,124; BD: 1,242; SCZ: 2,438, and AD: 16,225) and 24,196 controls we examined the association between psychiatric disease and mtDNA haplogroup in the Danish population. Psychiatric patients were identified from the Danish Psychiatric Central Registry. DNA was obtained from the Danish Neonatal Screening Biobank. Haplotyping was performed using the PGC developed PsychChip v.1.0. containing 418 SNPs in mtDNA. The SNP data were manually analysed and haplotyped according to haplogroup defining SNPs in Phylotree. Results Hg M was associated with affective disorder (n = 17260) with an OR of 0.47 (cfi.95%: 0.39 – 0.58) (p = 1*10–14), ADHD (n = 13395) with an OR of 0.50 (0.40 – 0.62)(p = 2*10–11). Among patients belonging to the macro-hg N, patients with schizophrenia (n = 2589), had a high proportion of hg A (n = 45), OR: 4.52 (cfi.95%: 3.0 – 6.7)(p = 1.2*10–12). No significant associations between mtDNA hgs and BD or ASD were found. In a mitoGWAS for all six conditions, three mitoSNPs were highly associated with affective disorder (p-values ranging from 2*10E-25 – 2*10E-21), ADHD (p-values: 2*10E-11 – 1*10E-10), and anorexia (p-values: 6*10E -8 - 6*10E-7) and another mitoSNP with schizophrenia (p = 2*10–11). Discussion Psychiatric disease seems to be bigenomic diseases with contributions from both the mitochondrial and nuclear genome. Haplogroup A is a risk factor for schizophrenia and haplogroup M is a protective factor for ADHD and affective disorder. However, both hgs A and M are infrequent in the Danish population and markers of Greenlandic and Asian origin, respectively. So it will be important through studies of interaction between mtDNA and the genomic DNA to precisely define the role of each of these factors in the etiology of psychiatric disease.

Optimization of Reactive Power Compensation Based on Fuzzy Mathematics

This paper proposes a heuristic method for optimization of reactive power compensation. Firstly, two fuzzy sets of node voltage and cost savings are formed. The compensation location with the greatest compensation suitability is obtained by fuzzy reasoning. Considering the operation modes of several different loads, the mathematical model of reactive power compensation optimization is established, and fuzzy multi-objective optimization is adopted. The method solves the fixed and variable compensation capacity, and calculates the compensation capacity for each existing compensation position cycle until the change does not occur. The above process is repeated until the new compensation position is no longer saved, and finally all the compensation positions, capacity and total savings can be obtained. The example analysis shows the effectiveness and practicability of the method.

Cross-layer design and optimization techniques in wireless multimedia sensor networks for smart cities

The future smart cities vision can be developed through leveraging the potentials of Internet of Things (IoT) and wireless sensor network (WSN) technologies. WSN is a resource constrained network where network nodes are tiny devices that are run on battery power. Diverse types of applications such as environmental and habitual monitoring, detection, and tracking, use WSNs. The invention of new network protocols, the establishment of new models for communications, and testing the available solutions in real world environment are some of the current research issues in WSNs. Main challenges in such networks include energy conservation in an efficient way, dealing with variable channel capacity, and the resource constrained nature of such networks. The design of architecture for such networks has a vital role in solving the issues to some extent, i.e., the cross layer design approach is an architectural technique that offers the interaction of different layers together to enhance the performance, minimize the energy consumption, enhance the network life time, and provide Quality of Service (QoS) in real time communications. These are some of the current areas where cross-layer design approaches are being used. This paper presents different types of cross-layer design techniques in wireless multimedia sensor networks. Using such architectural techniques, different state of the art cross-layer optimization approaches are discussed while giving the reader an insight on prominent challenges and issues along with future directions.

A thermodynamic closure for the simulation of multiphase reactive flows

A simple thermodynamic closure for the simulation of multiphase reactive flows is presented. It combines a fully explicit thermodynamic closure appropriate for weakly thermal multiphase flow simulations, with the classical variable heat capacity ideal gas thermodynamic closure, commonly used for reactive flows simulations. Each liquid and gas component is assumed to follow the recent Noble-Abel Stiffened Gas equation of state, fully described by a set of five parameters. A new method for setting these parameters is presented and validated through comparisons with NIST references. Comparisons with a well-known cubic equation of state, Soave-Redlich-Kwong, are also included. The Noble-Abel Stiffened-Gas equation of state is then extended as to cope with variable heat capacity, to make the mixture thermodynamic closure appropriate for multiphase reactive flows.

Activated CLL B Cells Variably Modulate microRNA-155 Levels in Naïve CD4+ T Cells, and the Direction and Magnitude of microRNA-155 Change Correlates with Th17 Levels and Clinical Course

T-helper 17 (Th17) cells constitute a subset of T cells that characteristically secrete IL-17. In addition to their normal adaptive immune functions, Th17 cells also play roles in supporting dysfunctional immune responses found in autoimmunity and cancer. Several studies suggest that Th17 cells play a protective role in chronic lymphocytic leukemia (CLL). For example, CLL patients exhibit varied levels of circulating Th17 cells, and elevated levels positively correlate with better clinical outcome regardless of IGHV-mutation status. To understand this relationship and elucidate the cellular and molecular mechanisms of Th17 generation in CLL, in particular the role of microRNAs known to affect Th17 development, we investigated cross-talk between naïve CD4+ T cells and CLL B cells. Moreover, since intraclonal leukemic B-cell subpopulations differing in time since cell birth/division can exhibit different functional effects on antigen presentation, we explored the effect of B-cell activation on this T - leukemic B-cell dialogue and how it affects the generation of Th17 cells.To determine potential candidates differentially expressed in CLL, we conducted genome-wide single-cell expression analysis comparing fluorescence activated cell sorting (FACS)-purified mature Th17 cells (CD3+/CD4+/CD45+/CD161+/CCR6+/ CCR4+/CXCR3-) from CLL patients and healthy donors. Selected candidate genes met the criteria of >7-fold increase in expression in CLL, adjusted p-value <1.5 x 10-6, and link to lymphocyte biology. Among selected candidates, microRNA-155 (miR-155), a critical regulator of Th17 differentiation, was found. Follow-up real time, quantitative PCR (RT-qPCR) analyses indicated a significant increase (P < 0.01) in miR-155 expression in CLL Th17 cells as compared to Th17 cells from healthy controls. Since there was no difference in expression between naïve T cells (CD3+/CD4+/CD62L+/CD45RO-) cells, this suggested a CLL-unique mechanism of miR-155 modulation.To determine whether CLL cells directly influence miR-155 levels in naïve CD4+ T cells, co-culture experiments using autologous leukemic or healthy B cells were carried out. FACS-purified peripheral blood naïve CD4+ T cells and B cells from CLL patients and from age-matched healthy controls were co-cultured for 3 days, and expression of T-cell miR-155 was determined by RT-qPCR. In the presence of unstimulated CLL or healthy B cells, miR-155 expression in naïve T cells remained unchanged across all co-cultures. However, upon activation, healthy and leukemic B cells exerted differential effects on miR-155 expression in autologous naïve T cells. In the presence of autologous healthy B cells pre-activated with CpG-ODN2006 and IL-15, miR-155 expression in healthy naïve T cells was significantly increased (P = 0.0313) across all samples. Conversely, CLL naïve T cells co-cultured with autologous, pre-activated leukemic B cells showed heterogeneous modulation of miR-155. Of interest, the magnitude and direction of miR-155 changes in the autologous CLL co-cultures positively correlated not only with circulating Th17 levels (P = 0.019), as determined by flow cytometry, but also with patient time to first treatment (P = 0.0003). Moreover, when samples were divided into 2 groups based on an increase or decrease in miR-155 levels after exposure to activated compared to resting CLL B cells, a significant difference was seen with median survival of 237 months and 67 months, respectively (P = 0.005). Consistent with previous observations from our lab, this correlation was independent of various prognostic markers, including IGHV-mutation status.Our results suggest the existence of a miR-155 modulatory mechanism mediated by CLL B cells that differs based on leukemic B-cell activation state and the degree of change occurring when naïve T cells are exposed to resting vs. activated B cells. Moreover, this variable effect in CLL patients differs from that in normal individuals, and the effect influences number of Th17 cells and patient outcome. Studies are underway to determine the effects that leukemic B cells, unstimulated or CpG-ODN2006 + IL-15 stimulated, have on autologous naïve T-cell maturation into Th17 cells, and the extent that this process depends on the variable miR-155 modulatory capacity of leukemic B cells. DisclosuresChiorazzi:Janssen, Inc: Consultancy; AR Pharma: Equity Ownership.

Impact of deep wind power penetration on variability at load centers

Increasingly, variable renewable energy capacity will be added distant from load centers in much of the world. How such intraregional heterogeneity in variable supply and load will impact the energy system in a deep renewable penetration scenario is studied here. Heterogeneous reliability requirements imposed by such scenarios are not well understood. Some unique geographic settings, such as the Nordic grid with weeks of pumped hydro backup, manage to circumvent this issue without significant curtailment, but most regions have yet to achieve the renewable energy levels at which the issue will arise. Using simulations of wind power expansion in New York State, we illustrate the intraregional effects by quantifying the net load, net load ramping, operating reserve and regulation requirements, and the associated distribution of infrastructure investments and ancillary services. The study finds that only at wind capacities exceeding 100% of the average statewide load does the wind-generated electricity meet significant portions of the distant demands. However, the peak net load in these areas is not reduced, requiring that dispatchable generation capacity be maintained. Moreover, the net load becomes highly variable, with large ramp rates that increase ancillary service requirements (operating reserves and frequency regulation) to ensure reliable system operation. A major finding is that the additional ancillary service requirements become more concentrated in the distant load centers. A second significant finding is that while transmission capacity upgrades greatly increase the wind-generated electricity that reaches load centers, the increased variability in that supply can exacerbate both the magnitude and heterogeneity of ancillary service requirements. These services would presumably be provided by the same local dispatchable resources that would now be operating at lower capacity factors but with higher variability. Such changes in the scale and distribution of intraregional integration measures and infrastructure investments may require new energy planning approaches and market structures to achieve anticipated future renewable energy targets.

Alternative approach for vehicle trajectory reconstruction under spatiotemporal side friction using lopsided network

Limitation of probe sensor-based technique to collect traffic data in the temporal domain tends to combine it with the fixed sensor. This combination technique involves extra equipment installation difficulties when the road segment becomes non-homogeneous due to traffic operations or lane configurations. Particularly, in developing countries, chaotic traffic pattern and the absence of a fixed sensor in the roadway create the trajectory reconstruction even more challenging. Video-sensor (also, other fixed-sensor) based trajectory reconstruction techniques require sensors for each non-homogeneous road segment and need separate fundamental diagram (FD) to estimate the required traffic parameters. These difficulties can be overcome by using probe sensors. Thus, this research proposes an approach of estimating traffic parameters from probe data considering variable road capacity. Those parameters are used as input to reconstruct the trajectories of all vehicles in the traffic stream (i.e. also non-probe vehicles, in particular) through the application of a lopsided network. The proposed approach improves the percent root mean square error of estimated travel time by around 38% compared with that which uses traffic parameters obtained from FD with respect to ground-truth travel time. This approach is very appropriate, economical and reliable, especially where the required number of fixed sensors is unavailable.

Development of the DayCent-Photo model and integration of variable photosynthetic capacity

We integrated a photosynthetic sub-model into the daily Century model (DayCent) to improve the estimations of seasonal changes in carbon fluxes at the Niwot Ridge LTER site and the Harvard forest LTER site (DayCent-Photo). The photosynthetic sub-model, adapted from the SIPNET/PnET family of models, includes solar radiation and vapor pressure deficit controls on production, as well as temperature and water stress terms. A key feature we added to the base photosynthetic equations is the addition of a variable maximum net photosynthetic rate (Amax). We optimized the parameters controlling photosynthesis using a variation of the Metropolis-Hastings algorithm along with data-assimilation techniques. The model was optimized and validated against observed net ecosystem exchange (NEE) and estimated gross primary production (GPP) and ecosystem respiration (RESP) values for AmeriFlux sites at Niwot Ridge and Harvard forest. The inclusion of a variable Amax rate greatly improved model performance (NEE RMSE = 0.63 gC·m–2, AIC = 2099) versus a version with a single Amax parameter (NEE RMSE = 0.74 gC·m–2, AIC = 3724). DayCent-Photo was able to capture the inter-annual and seasonal flux patterns for NEE, GPP, ecosystem respiration (RESP), and daily actual evapotranspiration (AET), but tended to overestimate yearly NEE uptake. The DayCent-Photo model has been successfully set up to simulate daily NEE, GPP, RESP, and AET for deciduous forest, conifer forests, and grassland systems in the US using AmeriFlux data sets and has recently been improved to include the impact of UV radiation surface litter decay (DayCent-UV). The simulated influence of a variable Amax rate suggests a need for further studies on the process controls affecting the seasonal photosynthetic rates. The results for all of the forest and grassland sites show that maximum Amax values occurs early during the growing period and taper off toward the end of the growing season.

A restorable fragile watermarking scheme with superior localization for both natural and text images

In this paper, we present a method for detecting and restoring tampered information in natural and text images. To take the detection ability, invisibility, and recovery quality into account for both natural and text images, this work generates the authentication watermark for each 4 × 4 block by a hash function and a variable capacity recovery watermark for each 2 × 2 block by allocating more bits to the textural blocks and fewer bits to the smooth ones. The authentication watermark and the recovery one are embedded in the original image by adopting different strategies based on a secret key. The multi-stage neighbor detection strategy is designed to locate the tampered image blocks accurately. The proposed scheme outperforms in invisibility, with detecting tampered locations and recovery of the tampered regions. The simulation results show that the proposed scheme achieves better recovery quality and invisibility for natural and text images due to a variable-capacity recovery watermark and superior localization. Further, the proposed method computationally is less expensive compared with the existing works.

An optimization model for quadratic flow thinning – a traffic protection mechanism for FSO networks

Flow thinning (FT) is an active traffic protection mechanism destined for communication networks with variable capacity of links, for example wireless networks. In FT, end-to-end traffic demands are equipped with dedicated logical tunnels (for example MPLS tunnels) whose maximal capacities are subject to thinning in order to follow the fluctuations of the currently available link capacities. It follows that for each demand the instantaneous traffic realized between its end nodes must accommodate to the current total capacity available on its dedicated tunnels. In the paper we develop an optimization model for network dimensioning for an applicative modification of FT, the so called Quadratic Flow Thinning (QFT), and present a solution algorithm based on the path generation method. We derive relevant pricing problems for basic variants of the QFT mechanism (and for its special case Affine Flow Thinning, AFT), and present a numerical study that illustrates efficiency of the optimization algorithm, as well as compares the network cost for different variants of QFT and AFT.

Energy Saving Systems of Hydrostatic Drives for Ship Deck Machines

Abstract A control system with a proportional directional throttling control valve or a directional control servo valve, controlling a cylinder (linear hydraulic motor) is used in the ship steering gear drive, in the controllable pitch propeller control, in the variable capacity pump control system for hydraulic deck equipment motors or fixed pitch propellers in small ships (for example ferries). Energy savings in a constant capacity pump operation can be achieved by means of overflow valve controlled by the oil outlet pressure between the directional throttling control valve and the cylinder. Although structural volumetric losses cannot be eliminated in such a system, but it is possible to reduce considerably structural pressure losses, mechanical losses and volumetric losses in the pump, and mechanical losses in the cylinder too. The paper discusses these energy savings using an earlier developed by Paszota mathematical model of losses in elements, the energy efficiency of the system and the operating range of the cylinder. The paper also presents a comparison of the energy behavior of two widespread structures of hydrostatic systems: a standard individual systems with a throttling steering fed by a constant capacity pump. Both system solutions are described and equations of the total efficiency η of the system are presented. Diagrams of energy efficiency of two hydraulic systems working at the same parameters of a speed and a load of hydraulic linear motor, which were different due to structure and ability of energy saving, were presented and compared.

What happens to groundwater ecosystems when you take out the groundwater?

The removal of groundwater results in the lowering of water tables, which, for groundwater organisms, translates to reduced habitat availability and changed environmental conditions in the habitat that remains. While changes in groundwater levels may be well modelled and predicted, the impacts on groundwater ecosystems remain poorly known. There are three key processes associated with groundwater drawdown in shallow alluvial aquifers that may threaten groundwater ecosystems. These processes are 1. the physical decline of water levels, from which fauna can be stranded in isolated or unsaturated sediments; 2. the loss of or change to habitat, particularly as water levels move through different geological strata and 3. changes in hydrological connectivity, that may influence water quality as a result of increasing distance or disconnection from the surface and other water sources. Results from laboratory studies show the variable capacity for stygobiotic invertebrates to move with declining water tables, dependent on both drawdown rate and sediment attributes. Once isolated in unsaturated habitats, our tests show that survival of fauna is limited beyond 48 h. Invertebrates are constrained by sediment size and unable to use those with relatively small pore spaces and may not be able to use all available saturated habitats. This talk will present a framework that identifies the key threats of groundwater drawdown to groundwater ecosystems and will highlight the current state of knowledge of each of these threatening processes. We present the results of empirical studies on the response of stygobiotic invertebrates to specific elements of the framework.

Estradiol to Androstenedione Ratios Moderate the Relationship between Neurological Injury Severity and Mortality Risk after Severe Traumatic Brain Injury.

Early declines in gonadotropin production, despite elevated serum estradiol, among some individuals with severe traumatic brain injury (TBI) suggests amplified systemic aromatization occurs post-injury. Our previous work identifies estradiol (E2) as a potent mortality marker. Androstenedione (A), a metabolic precursor to E2, estrone (E1), and testosterone (T), is a steroid hormone substrate for aromatization that has not been explored previously as a biomarker in TBI. Here, we evaluated serum A, E1, T, and E2 values for 82 subjects with severe TBI. Daily hormone values were calculated, and E2:A and E1:T ratios were generated and then averaged for days 0-3 post-injury. After data inspection, mean E2:A values were categorized as above (high aromatization) and below (low aromatization) the 50th percentile for 30-day mortality assessment using Kaplan-Meier survival analysis and a multivariable Cox proportional hazard model adjusting for age, and Glasgow Coma Scale (GCS) to predict 30-day mortality status. Daily serum T, E1, and E2 were graphed by E2:A category. Serum E1 and E2 significantly differed over time (p < 0.05); the high aromatization group had elevated levels and a significantly lower probability of survival within the first 30 days (p = 0.0274). Multivariable Cox regression showed a significant E2:A*GCS interaction (p = 0.0129), wherein GCS predicted mortality only among those in the low aromatization group. E2:A may be a useful mortality biomarker representing enhanced aromatization after TBI. E2:A ratios may represent non-neurological organ dysfunction after TBI and may be useful in defining injury subgroups in which GCS has variable capacity to serve as an accurate early prognostic marker.

Study on a novel variable capacity technology and control strategy for refrigerated shipping container unit

A novel variable capacity system based on variable frequency compressor combined hot-gas bypass technology, was developed in the refrigerated shipping container unit. Then, numerical study had been carried out on control strategy for the variable capacity system. The schematic of variable capacity control in chilled mode/frozen mode was presented respectively. The detailed control models for the electronic expansion valve, inverter compressor, electronic hot-gas valve were developed. Finally, the novel variable capacity technology and control strategy was implemented in the experimental refrigeration unit system. Experimental tests for the refrigeration unit were carried out. The results of the experimental tests showed that in the refrigeration unit system, the novel variable capacity technology and control strategy based on combining variable frequency compressor with hot gas bypass technology, which could keep the inner temperature more stable. Therefore, the novel variable capacity technology and control strategy have been proved to be workable.

Pengaruh Kapasitas Sumber Daya Pegawai Negeri Sipil, Komitmen Organisasi dan Pemanfaatan Teknologi Informasi Terhadap Penerapan Pengendalian Intern Kas Pada Satuan Kerja Perangkat Daerah (SKPD) di Lingkungan Pemerintah Kota Banda Aceh

This study aims to examine the effect of human resource capacity and organizational commitment on the application of cash internal controls at the Regional Work Unit in the Banda Aceh City Government. The population in this study amounted to 36 SKPD and 108 respondents who were self from the Head of Service / Head of Agency / Head of Office as Budget Leaders and Users, SKPD Financial Administration Officers (PPK-SKPD) who examined payment request documents and made books on each SKPD cash expenditure , Treasurer of expenditure, Treasurer of receipt if there is cash receipt in the SKPD. Because of this research population, the nature of this research is census. The analytical method used in this study is multiple linear regression. The results of this study indicate simultaneously and partially the variable capacity of civil servant resources, organizational commitment and utilization of information technology affect the implementation of internal cash controls

Development and tests of a loop heat pipe with several separate heat sources

The paper presents the results of development and experimental investigations of ammonia loop heat pipe (LHP) intended for a simultaneous cooling of several heat sources dissipating a variable capacity. The LHP was equipped with two heat exchangers located on the liquid line and one heat exchanger on the vapor line, which were in thermal contact with some additional heat sources. The LHP evaporator was in thermal contact with the main, the most powerful heat source. It has been shown that at a nominal heat load of 120 W on the main heat source the total heat load on the additional heat sources located on the liquid line may reach 34 W. The maximum heat load on an additional heat source located on the vapor line, in the same conditions, was 9 W. It has also been shown that a thermal action on the liquid line has a considerable effect on the temperature of the main heat source, whereas a thermal action on the vapor line does not influence it.

Impacts of two-stage deterioration on an integrated inventory model under trade credit and variable capacity utilization

The joint economic lot sizing problem (JELP) model provides a global view to facilitate the development of a production-inventory policy for an integrated system. However, when a deteriorating item is involved, previous studies have neglected the following two important issues: (1) the deterioration quantity increases the demand for the supplier's capacity, which consequently requires the supplier to recalculate the corresponding average cost and reevaluate the capacity utilization, and (2) given the supplier's production rate, in-transit deterioration imposes restrictions on the delivery distance or in-transit time. Therefore, the existing integrated policies may lead to infeasible solutions for the distribution channel when a deterioration item is included. In view of these two issues, a generalized JELP model under delay in payments is formulated to investigate the integrated production-inventory policy for an item with two-stage deterioration (in-transit and retail deterioration) while incorporating both transportation time and capacity utilization. By developing the average cost functions of the supply chain members and employing several new definitions (e.g., variable capacity utilization), this paper provides a mechanism for measuring the influence of two-stage deterioration on the supplier's capacity utilization for the JELP. Three algorithms are proposed to obtain optimal decisions based on the theoretical results. This paper demonstrates that the supplier's variable capacity utilization is relevant to transportation time and two-stage deterioration, which can be applied to evaluate the feasibility of the integrated production-inventory policy for the deteriorating item. Furthermore, there is a maximum allowable value for the retailer's order cycle.

Prey–Predator Models with Variable Carrying Capacity

Prey–predator models with variable carrying capacity are proposed. These models are more realistic in modeling population dynamics in an environment that undergoes changes. In particular, prey–predator models with Holling type I and type II functional responses, incorporating the idea of a variable carrying capacity, are considered. The carrying capacity is modeled by a logistic equation that increases sigmoidally between an initial value κ0&gt;κ1 (a lower bound for the carrying capacity) and a final value κ1+κ2 (an upper bound for the carrying capacity). In order to examine the effect of the variable carrying capacity on the prey–predator dynamics, the two models were analyzed qualitatively using stability analysis and numerical solutions for the prey, and the predator population densities were obtained. Results on global stability and Hopf bifurcation of certain equilibrium points have been also presented. Additionally, the effect of other model parameters on the prey–predator dynamics has been examined. In particular, results on the effect of the handling parameter and the predator’s death rate, which has been taken to be the bifurcation parameter, are presented.

DDoS Attacks Detection and Prevention in Mobile Adhoc Network: A Survey

Ad-hoc system is a gathering of wireless movable nodes enthusiastically creating a momentary network lacking the use of any core-existing centralized administration or network infrastructure. MANET has some limitations owing to infrastructure, mobility, capabilities of mobile nodes or due to system as a whole. Limitations due to infrastructure or system, Broadcast nature of communications, frequent disconnections / partitions, Limited bandwidth, packet loss due to transmission error, variable capacity links. Cooperative procedures, Exposed medium, dynamically varying system topology, inadequacy of centralized monitoring, Nonexistence of clear line of resistance. There is no layered security in MANETs like in wired network. Data packets routed between a sender node (source) and a receiver node (destination) of a MANET often traverse along a path spanning multiple links, which is known as the multihop path. The paper provides survey to DDoS attacks prevention and detection methods.

Experimental studies of a variable capacity direct-expansion solar-assisted heat pump water heater in autumn and winter conditions

A variable capacity direct-expansion solar-assisted heat pump (DX-SAHP) system was studied experimentally under the meteorological condition of Qingdao located in the East China area. It was mainly made up of a solar collector/evaporator, a variable-frequency rotary-type hermetic compressor, a micro-channel condenser, and an electronic expansion valve. A series of experiments were carried out, in order to evaluate the performance of the DX-SAHP system during the autumn and winter period, including the system coefficient of performance (COP), the electric power to the compressor, the evaporating and condensing pressures, and the discharge temperature of the compressor. Experimental results showed that for the base case considered in this study, under the sunny and overcast day conditions in the autumn, the average COP was higher than 4.0 and 3.0, respectively. Even in the extreme weather of the winter conditions, the average COP was also higher than 2.5. In general, with the increase of water temperature, the compressor speed increased gradually, and the corresponding electric power of the compressor increased sharply. The condensing pressure also increases, as does the discharge temperature of the compressor, while the evaporating pressure remains a relatively low level with smaller variations.