AC Unit Research Articles

Pipelined Viterbi Decoder Using FPGA

Convolutional encoding is used in almost all digital communication systems to get better gain in BER (Bit Error Rate) and all applications needs high throughput rate. The Viterbi algorithm is the solution in decoding process. The nonlinear and feedback nature of the Viterbi decoder makes its high speed implementation harder. One of promising approaches to get high throughput in the Viterbi decoder is to introduce a pipelining. This study applies a carry-save technique, which gets the advantage that the critical path in the ACS feedback becomes in one direction and get rid of carry ripple in the Add part of ACS unit. In this simulation and implementation show how this technique will improve the throughput of the Viterbi decoder. The design complexities for the bit-pipelined architecture are evaluated and demonstrated using Verilog HDL simulation. And a general algorithm in software that simulates a Viterbi Decoder was developed. Our research is concerned with implementation of the Viterbi Decoders for Field Programmable Gate Arrays (FPGA). Generally FPGA's are slower than custom integrated circuits but can be configured in the lab in few hours as compared to fabrication which takes few months. The design implemented using Verilog HDL and synthesized for Xilinx FPGA's.

Krankenhaushygiene - Raumlufttechnische Anlagen und Warmluftdecken in Operationssälen

Nowadays almost all operating rooms are equipped with air conditioning (AC units). Their main purpose is climatization, like ventilation, moisturizing, cooling and also the warming of the room in large buildings. In operating rooms they have an additional function in the prevention of infections, especially the avoidance of postoperative wound infections. This is achieved by special filtration systems and by the creation of specific air currents. Since hypothermia is known to be an unambiguous factor for the development of postoperative wound infections, patients are often actively warmed intraoperatively using warm air blankets (forced-air warming units). In such cases it is frequently discussed whether such warm air blankets affect the performance of AC units by changing the air currents or whether, in contrast, have exactly the opposite effect. However, it has been demonstrated in numerous studies that warm air blankets do not have any relevant effect on the functioning of AC units. Also there are no indications that their use increases the rate of postoperative wound infections. By preventing the patient from experiencing hypothermia, the rate of postoperative wound infections can even be decreased thereby.

Model predictive HVAC load control in buildings using real-time electricity pricing

We propose a practical cost and energy efficient model predictive control (MPC) strategy for HVAC load control under dynamic real-time electricity pricing. The MPC strategy is built based on a proposed model that jointly minimizes the total energy consumption and hence, cost of electricity for the user, and the deviation of the inside temperature from the consumer's preference. We develop an algorithm that assigns temperature set-points (reference temperatures) to price ranges based on the consumer's discomfort tolerance index. We also design a practical parameter prediction model for the mapping between the HVAC load and the inside temperature. The prediction model and the produced temperature set-points are integrated as inputs into the MPC controller, which is then used to generate signal actions for the AC unit. To investigate and demonstrate the effectiveness of our approach, we present a simulation based experimental analysis using real-life pricing data. The experiments reveal that the MPC strategy can lead to significant reductions in overall energy consumption and cost savings for the consumer. Results suggest that by providing an efficient response strategy for the consumers, the proposed MPC strategy can enable the utility providers adopt efficient demand management policies using real-time pricing.

On the Need for Energy Labeling for Villa Air Conditioners in Saudi Arabia and its Economic and Environmental Impact

The present article discusses the need for energy labeling for villa air conditioners in Saudi Arabia. The article aims at raising the public awareness about energy savings and its economical and environmental impact in Saudi Arabia as one of the largest producers and exporters of the oil in the world. In light of comprehensive literature, market and consumer's surveys, a plan for implementing and enforcing Minimum Energy Performance Standards (MEPS) with gradually increasing MEPS over a period of 15 years, in addition to a one transition year, has been proposed. The economical and environmental impact of the proposed plan on the national economy and environment has been analyzed and presented. The analysis revealed that improving the villa AC units' energy efficiency ratio (EER) according to the proposed plan can save up to $ 59.12 billion (based on the average oil prices of 2010) and can reduce the Carbon Dioxide emission by 177.21 million tons over the first 16 years of implementing the plan. The legislative and financial support required to make the implementation and enforcement of the proposed plan possible has been outlined and discussed.

Study on the effect of preference of air-conditioning usage on the exergy consumption pattern within a built environment

According to previous work, preference is one major factor influencing occupants' behaviour. This paper aims at identifying the magnitude preference on the exergy consumption pattern within a built environment. The comparison is made between one group claiming to like sleeping in air–conditioned spaces and the other claiming to dislike it. In conclusion, the exergy analysis showed that at the individual level, preference accounts for an exergy consumption rate up to 15% higher and that, at the community level, the exergy consumption rate of those preferring the AC–unit use is up to four times higher than that of the others'.

Synthesis and Reversal Activity of Multidrug Resistance of Hepatocellular Carcinoma of (−)-Epigallocatechin Gallate Analogues

Aim To investigate the reversal activity and structure-activity relationship of (−)-epigallocatechin gallate (EGCG) analogues on the multidrug-resistant tumor cells. Methods (−)-Epigallocatechin gallate analogues were synthesized and confirmed by 1H, 13C NMR and 2DNMR data. MTT method was used to evaluate their cytotoxicities against human normal hepatocellular cells LO2, hepatic carcinoma cells BEL-7402, and the hepatic carcinoma 5-FU-resiatant cells BEL-7402/5-FU. Results 5, 7, 3′, 4′, 5′, 3″, 4″, 5″-octa-acetyl-EGCG (AcEGCG), 5, 7, 3′, 4′, 3″, 4″, 5″-hepta-acetyl-ECG (AcECG), 7, 3′, 4′, 5′, 3″, 4″, 5″-hepta-acetyl-EGCG (Ac-A), and 3′, 4′, 5′, 3″, 4″, 5″-hexa-acetyl-EGCG (Ac-B) were synthesized. Compounds Ac-A and Ac-B were reported for the first time. IC 50 of AcECG, Ac-A, and Ac-B against the BEL-7402 and BEL-7402/5-FU cells appeared to be lower than EGCG, whereas that of AcEGCG appeared to be lower than EGCG against the BEL-7402 cells, but much higher against the BEL-7402/5-FU cells. Although the peracetates of EGCG and AcEGCG significantly reversed the 5-FU resistant BEL-7402/5-FU cells, partly acetated EGCG, Ac-A and Ac-B showed weaker reversal effect, indicating that after the acetyl (Ac) was introduced to EGCG, the introduction of more Ac units will enhance the reversal activity. AcEGCG and AcECG, especially AcEGCG, showed significant reversal activity in BEL-7402/5-FU cells, while EGC showed only weak reversal effect. Conclusion The galloyl in EGCG could be necessary to its reversal activity. AcEGCG significantly increased the sensitivity of the BEL-7402/5-FU cells towards 5-FU and could be used as a potential reversal agent for drug-resistant tumor cells.

The use of CFD for predicting and optimizing the performance of air conditioning equipment

This paper reports on the use of CFD for predicting and improving the performance of a rooftop AC unit. The current work considered the hydrodynamic and thermal fields on the air flow side of the unit with exact modeling of fans and heat exchangers. This is in addition to predicting condensation on cooling coils. Because only the air flow side is considered, the evaporator and condenser compartments are decoupled and the solution in each section is established separately. In the evaporator compartment the flow is solved as a two-phase flow (gas and liquid) with the gas phase being composed of two species (dry air and water vapor). In the condenser section however, the flow is treated as a single phase flow. The exact modeling of heat exchangers and fans increased the grid size and computational cost, but resulted in realistic results and reliable model. A total of 31 million control volumes are used to model the evaporator and condenser sections. Results indicate the presence of several recirculation zones in the evaporator compartment. Sensible and latent cooling capacities for several design conditions predicted by the model are in close agreement with available experimental data. The differences between the total capacities predicted by the model in the evaporator section and those reported experimentally are within 2.7% for all cases considered. Predictions in the condenser section resulted in a load that is only 0.00136% different than the one calculated using experimental data. To improve the performance of the unit, six different modified designs of the evaporator coil are developed and tested. The newly modified designs are based on changing the coil inclination angle and/or number of fins per unit length for the same coil height and surface area. One of the designs resulted in 6.18% decrease in the cooling capacity, while the remaining modifications increased the cooling capacity by values ranging between 2.17% and 8.6%.

Inherent correlation between the total output cooling capacity and equipment sensible heat ratio of a direct expansion air conditioning system under variable-speed operation (XXG SMD SHR DX AC unit)

Appropriately controlling indoor air humidity at a suitable level in buildings is important. To simultaneously control both indoor air dry-bulb temperature and relative humidity requires the match between the total output cooling capacity of an A/C system and the total cooling load in a space served by the A/C system, as well as the Equipment sensible heat ratio (SHR) of the A/C system and the Application SHR of the conditioned space. This paper reports on an experimental study on the inherent correlations between the total output cooling capacity and Equipment SHR of a DX A/C system. Experiments were carried out under different combinations of compressor speed and supply fan speed, and also under different inlet air conditions to the DX evaporator. The results obtained would lead to a better understanding of the operating characteristics of a DX A/C system under variable-speed operation, as well as the constraint of using these characteristics in developing appropriate control strategies, so as to better design, operate and control DX A/C systems for improved indoor thermal environmental control.

Среда разработки и исследования систем автоматического управления технологическими процессами ASPC-LAB

There is a set-theoretic justification of ACS unit design, described the experience of practical implementation of software system based on the principles of free source code for the design and the ACS study complex systems

A microcontroller‐based soft‐starter for residential air‐conditioners: harmonic analysis

PurposeThe purpose of this paper is to reduce the inrush current and dip in voltage for energy‐ saving purposes in relation to residential air‐conditioning systems.Design/methodology/approachThe paper focuses on the experimental harmonic investigation of a window‐type residential AC unit line current under time‐based soft‐starting control strategy. The control strategy assumes that only source voltage and current measurements are available. The soft‐starter is based on power electronic devices controlled through a firing signal generated by a programmed microcontroller during the first 500 ms.FindingsThe harmonic content shows the effect of the soft‐starter in exciting high‐frequency components of the line current. Harmonics investigations show that the high frequencies – even or odd multiples – of the fundamental line frequency are all excited by the soft‐starter approach. Some of these frequencies may harm the life cycle of the air‐conditioner.Research limitations/implicationsThe real data harmonic analysis shows that the adopted approach excites the entire frequency spectrum of the signal. A better monitoring of the harmonics is required. A closed loop adaptive soft‐starting control may perform much better than a time‐based soft‐starting strategy.Originality/valueThe paper assesses the power quality related to time‐based soft‐starting strategy of a residential air‐conditioning system to reduce the inrush current and the dip in voltage, both with a serious effect on energy savings, especially when the AC load is around 65 per cent of the total power demand load.

Improving the Removal of Anions by Coagulation and Dissolved Air Flotation in Wastewater Reclamation

This study investigated the feasibility of improving the removal of anions from a secondary effluent by coagulation/flocculation (Coag/Floc) and dissolved air flotation (DAF) using a pilot-scale wastewater reclamation plant in a high-tech industrial park. The pilot plant was equipped with units of Coag/Floc, DAF, activated carbon beds (AC), micro-filtration modules (MF) and a reverse-osmosis membrane (RO). It was operated in-situ continuously for around one year to evaluate the performance of anion removal in two processes - the AC-RO process and the DAF-AC-RO process. Long-term experimental results indicated that combining Coag/Floc, DAF and AC units increased the potential of pretreatment to remove anions. The removal efficiencies in Coag/Floc-DAF units were in the order phosphate > fluoride > chloride > sulfate > silicate. The charged complex of PACl flocs revealed a higher affinity for adsorption onto phosphate and fluoride than on chloride, sulfate and silicate. Comparison of the performance of Coag/Floc-DAF-AC units in the DAF-AC-RO process with that of a single AC unit in the AC-RO process demonstrated that adding Coag/Floc-DAF units increased the removal efficiencies of phosphate, fluoride and silicate by approximately 70.0 %, 42.7 % and 70.1 %, respectively. Most of the phosphate and fluoride were removed in Coag/Floc-DAF units, while most of the silicate escaped from the Coag/Floc-DAF units, and was adsorbed and/or trapped in the AC unit. The quality of reclaimed water in the DAF-AC-RO process complied with the requirements of high-tech industries in cleaning processes. Combined units of Coag/Floc-DAF-AC were therefore recommended for use in pretreatment in wastewater reclamation in high-tech industrial parks.

Cover Picture: A Novel Mycolactone from a Clinical Isolate of Mycobacterium ulcerans Provides Evidence for Additional Toxin Heterogeneity as a Result of Specific Changes in the Modular Polyketide Synthase (ChemBioChem 4/2005)

The cover picture shows the structure (in red, right) of the lipophilic polyketide toxin mycolactone obtained from the reference Ghana strain of Mycobacterium ulcerans, the causative agent of the emerging disease Buruli ulcer, and that (in red, left) of a molecular variant of mycolactone newly identified from a clinical isolate of M. ulcerans from China. The new variant bears a single additional methyl group in the sidechain, as shown by mass spectrometry. Also shown at the top is the difference detected between the structural genes; this difference is dictated by a precise acyltransferase (AT) domain swap in the chain‐building polyketide synthase, so that a propionate (Pr) unit is recruited rather than an acetate (Ac) unit. Detailed information about this apparent natural example of polyketide biosynthetic engineering is reported by P. Leadley et al. on p. 643 ff.

Efficiencies of Traditional and Digital Measurement Technologies for Forest Operations

Abstract Higher-precision technologies may increase measurement accuracy and efficiency for operational layout while decreasing total planning costs. Although a number of trials have been completed on the potential implementation of some of these new technologies, few have quantified the benefits of such devices in an operational setting. Unit boundaries for 16 (∼1 ac) units were measured by three surveying techniques, comprising (1) a string box, manual compass, and clinometer; (2) a laser, digital compass, and digital data collector; and (3) a GPS. Collected data were compared to a fourth benchmark method established with a total station. Techniques were statistically analyzed and error distributions were developed at either a unit or an individual data-point scale. Time and cost studies were conducted to determine the overall efficiencies of each technique. Our results should assist forest resource managers in their decisions when selecting alternate measurement tools for collecting spatial data. West. J. Appl. For. 20(2):138–143.

An Efficient In-Place VLSI Architecture for Viterbi Algorithm

This paper presents a novel design of Viterbi decoder based on in-place state metric update and hybrid survivor path management. By exploiting the in-place computation feature of the Viterbi algorithm, the proposed design methodology can result in high-speed and modular architectures suitable for those Viterbi applications with large constraint length. This feature is not only applied to the design of highly regular ACS units, but also exploited in the design of trace-back units for the first time. The proposed hybrid survivor path management based on the combination of register-exchange and trace-back schemes cannot only reduce the number of memory operations, but also the size of memory required. Compared with the general hybrid trace-back structure, the overhead of register-exchange circuit in our architecture is significantly less. Therefore, the proposed architecture can find promising applications in digital communication systems where high-speed large state Viterbi decoders are desirable.

Fluorescence Properties, Induced-Fit Guest Binding and Molecular Recognition Abilities of Modified γ-Cyclodextrins Bearing Two Pyrene Moieties

Abstract γ-Cyclodextrin (γ-CD) derivatives bearing two pyrene moieties at AB, AC, AD, and AE glucose units (1–4), were prepared as chemosensors for detecting molecules by their guest-responsive excimer emission intensity. All these hosts exhibited predominant excimer emission and remarkable induced circular dichroism (ICD) in a 20% dimethyl sulfoxide aqueous solution. The excimer emission and the ICD intensities mostly decreased upon addition of a variety of organic guests. The result indicates that 1–4 undergo an induced fit conformational change upon complex formation, excluding the pyrene moieties from inside to outside the γ-CD cavity in guest binding. The guest-induced fluorescence variations were analyzed by 1 : 1 host–guest stoichiometry and the obtained binding constants were roughly correlated with the guest-induced fluorescence variations. The binding and fluorescence data revealed that 1–4 have remarkable molecular recognition abilities for bile acids and other guests.

Household ownership of electric room air conditioners

The rapid increase in the number of electric room air conditioners (AC units) per household, which may affect summer peak demand for electricity, may be due in part to their relatively low purchase prices. The present study attempted to measure the effects of purchase prices on the household's choice of the number of AC units, using a subsample of the 1992 survey by the Central Research Institute of Electric Power Industry in Japan. This survey provides data on residential AC-unit holdings and electricity consumption, which are used to estimate a probabilistic discrete choice model of residential AC units. The empirical results show that the cost of air conditioning has significant and adverse impacts on the choice of the number of AC units.

Cooperation between Core Binding Factor and Adjacent Promoter Elements Contributes to the Tissue-specific Expression of Interleukin-3

Tissue-specific expression of interleukin-3 (IL-3) is mediated via cis-acting elements located within 315 base pairs of the transcription start. This is achieved in part through the positive activities of the AP-1 and Elf-1 sites in the IL-3 promoter. The contribution to T cell-specific expression by other promoter sites was assessed in a transient expression assay with IL-3 promoter constructs linked to a luciferase gene, focusing initially on the core binding factor (CBF) site, which is footprinted in vivo upon T cell activation. Activity of the CBF site is shown to be critically dependent on the adjacent activator site Act-1. Together the Act-1 and CBF sites form a functional unit (AC unit) with dual activity. The AC unit is demonstrated to enhance basal activity of promoters both in fibroblasts and T cells. This activity is further inducible in activated T cells, but not in fibroblasts. In addition to the already identified NIP repressor site, evidence is presented for a second repressor region that restricts promoter activity in fibroblasts. Finally, a novel positive regulatory element has been mapped in the IL-3 promoter between nucleotide -180 and -210 that leads to increased expression in T cells. Together these results demonstrate that T cell expression of IL-3 is not specified by the activity of a single tissue-specific element, but instead involves multiple interacting elements that provide both specific positive regulation in T cells and specific negative regulation in fibroblasts.

Injury to Wild Brook Trout by Backpack Electrofishing

Most studies of salmonid injuries caused by electrofishing have been conducted on adult brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss in medium- or high-conductivity waters. The objective of this study was to assess internal injuries of wild brook trout Salvelinus fontinalis that were captured with AC and pulsed-DC backpack electrofishing units in four small, low-alkalinity streams. We used X rays and autopsies to assess the injury rate of 579 brook trout (95–237 mm total length, TL) captured by electrofishing. Injuries consisted of either internal hemorrhages, spinal misalignment and fracture, or both. We found a total of 74 hemorrhages and 91 spinal injuries. Injury rates of brook trout captured by electrofishing were not significantly different (P > 0.05) between electrical wave forms: 26% for AC and 22% for pulsed DC. Injury rate increased with fish length, ranging from 14% for fish smaller than 125 mm TL to 42% for fish 175 mm TL or larger. In spinal-injured fish, damage occurred to an average of six vertebrae, usually ones in the posterior region of the spinal column between the dorsal and anal fins. We also examined 89 brook trout (87–225 mm TL) captured by angling. Less than 7% of the angled fish had injuries, all detected by X ray. We conclude that the incidence of electrofishing-induced injury can be substantial, even for relatively small brook trout in low-alkalinity waters. The relation of these injuries to mortality remains to be explored.

Imaging of zeolite surface structures by atomic force microscopy

Atomic force microscopy has been employed to study the (010) surface structure of the natural zeolite heulandite. Images on a macroscopic scale exhibit large terraces separated from each other by half of the unit cell length b. Molecular resolution is obtained when measured in 0.1M NaOH. The surface ac unit cell is about 26% larger in area than the bulk unit cell.

Imaging of zeolite surface structures by atomic force microscopy

Atomic force microscopy has been employed to study the (010) surface structure of the natural zeolite heulandite. Images on a macroscopic scale exhibit large terraces separated from each other by half of the unit cell length b. Molecular resolution is obtained when measured in 0.1M NaOH. The surface ac unit cell is about 26% larger in area than the bulk unit cell.