Wireless Communication

In the wireless communication, contact with life is a significant test of a wireless body area network, and it is limited by power and small sensor nodes (Deshpande & Kulkarni, 2017).

From: Recent Advancement of IoT Devices in Pollution Control and Health Applications, 2023

Wireless Communications

Michele Zorzi, A. Chockalingam, in Encyclopedia of Physical Science and Technology (Third Edition), 2003

V.E Energy and Power Management

Battery life has always been a concern in the wireless communications industry, since improved battery performance translates in smaller and lighter devices. Unfortunately, the rate at which battery performance improves (in terms of available energy per unit size or weight) is fairly slow, despite the great interest generated by the booming wireless business. Other means to reduce power consumption in wireless devices have therefore been receiving interest in the research community. Besides the traditional search for better circuits and power amplifiers, which directly improve the power consumption efficiency of the whole device, some recent research results have taken a broader view of the problem. In particular, it has been recognized that energy conservation is a task which can be performed at multiple levels, and energy-efficient protocol design criteria can be identified and applied. This concept has resulted in studies on energy-efficient error control schemes (where bad channel conditions cause the transmitter to enter a sleep mode), multiple-access protocols (by minimizing collisions and the need for retransmission), software techniques (such as various low-power modes at the operating system level), and signal processing algorithms (via more careful software circuit design). Another traditional topic for wireless communications, namely power control, has been recently revisited in a network resource allocation perspective (as opposed to simple attenuation compensation), opening up new optimization problems and networking issues. Advances on these topics can be found in (IEEE, 1995a,; Bambos and Rulnick, 1997; Sivalingam et al., 1997; Zorzi and Rao, 1997; and Chockalingam and Zorzi, 1998).

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BATTERIES | Dynamics

A. Jossen, in Encyclopedia of Electrochemical Power Sources, 2009

Modern battery applications such as wireless communication systems or hybrid electric vehicles operate at high power fluctuations. For some applications where the power frequencies are high (above some 10 or 100 Hz), it is possible to filter the high frequencies using passive components; yet this results in additional costs. In other applications where the dynamic time constants are in the range up to a few seconds, filtering cannot be done. Batteries are hence operated with the dynamic loads. But what happens under these dynamic operation conditions?

This article describes the fundamentals of the dynamic characteristics of batteries in a frequency range from a few megahertz down to the millihertz range. As the dynamic behavior depends on the actual state of charge (SoC) and the state of health (SoH), it is possible to gain information on the battery state by analyzing the dynamic behavior.

High dynamic loads can influence the battery temperature, the battery performance, and the battery lifetime.

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Cognitive radio

Jianjun Zhang, Jing Li, in Spatial Cognitive Engine Technology, 2023

1.1 Introduction

With the continuous growth of wireless communication services, the demand for wireless services (such as mobile communications, public safety, radio, and television) continues to increase, making wireless spectrum an important national resource in modern society. Available frequency bands are tightening and the lack of spectrum resources is becoming serious. However, is there really a shortage of spectrum?

In essence, the shortage of spectrum exists mainly because the use of wireless spectrum resources is managed and coordinated by the national government, and the fixed spectrum management policy has caused the problem of serious shortage of spectrum resources in the use of wireless spectrum. Except for the very few industrial, scientific, and medical frequency bands, the frequency use policies of countries around the world mostly adopt a license system. However, not all licensed users occupy the licensed frequency bands continuously. Some frequency bands are not employed by users part of the time and some are occupied occasionally. Even if the system spectrum utilization rate is low, it is still unable to allocate the space spectrum to other systems, that is, it is unable to achieve spectrum sharing. Studies have shown that at any given moment, the spectrum used by people accounts for only 2% to 6% of all available spectrum, so wireless communications face the problem of the shortage and waste of spectrum resources.

The root of this problem is that existing wireless communication technology is difficult to adapt to the dynamic changes of the environment. Cognitive science theory provides a good idea for solving this problem. Cognitive science studies the information processing of human perception and thinking, including from sensory input to solving complex problems, and from human individuals to the intelligent activities of human society and the nature of human intelligence and machine intelligence. The cognitive system makes plans, decisions, and executions through observation and learning of the environment, so that the system adapts to the dynamically changing environment [1].

To solve the problem of the insufficient radio-frequency spectrum, the concept of cognitive radio was clearly proposed for the first time in IEEE Personal Communications journal in Aug. 1999 by a consultant for MITRE, Professor Joseph Mitola of the Royal Swedish Institute of Technology. In a broad sense, cognitive radio means that the wireless terminal has sufficient intelligence or cognitive ability to detect, analyze, learn, reason, and plan the history and current conditions of the surrounding wireless environment, and to use the corresponding results to adjust its own transmission parameters. The most suitable wireless resource completes the wireless transmission. Cognitive radio systems employ unused spectrum holes in licensed frequency bands to improve spectrum use and effectively employ various idle channels in different regions and many time periods. This technology was quickly adopted as a possible solution to deal with the spectrum resource crisis. Cognitive radio uses this frequency band to send signals when it detects that a specific authorized frequency band is not used within a specific range, and to ensure that it does not cause significant interference to the transmission of authorized users.

After the concept of cognitive radio was proposed, the US Federal Communications Commission (FCC) opened an additional part of the authorized spectrum to commercial applications, pointing to the need to adopt cognitive radio technology, and established the Wireless Spectrum Policy Task Force in Jun. 2002 to formulate the work policy of smart wireless communications. This policy uses a number of technologies such as cognitive radio, avoids channels in use, and dynamically allocates frequencies. In Dec. 2003, the FCC announced an amendment to Chapter 15 of the FCC Rules (Rule Part l5), which is equivalent to the Radio Wave Act of the United States. Terminals can also use existing wireless frequency bands that need to be licensed. It also legalized the use of cognitive radio in the 5-GHz and TV frequency bands, laying the foundation for the development of cognitive radio.

In 2003, Raytheon, which is engaged in developing high-end military equipment, accepted the contract for the development of the Next Generation Communication (XG) program from the Defense Advanced Planning Agency. The goal of the XG plan is to solve the problem of opportunistic spectrum access comprehensively. In terms of top-level design, the plan has two sets of goals: to develop technologies that can achieve opportunistic spectrum access, and to achieve flexibility in strategies to apply a framework structure. Fig. 1.1 shows the XG plan based on cognitive radio [2].

Figure 1.1. XG plan based on cognitive radio.

The XG plan is an autonomous dynamic spectrum use plan. It perceives a wider frequency band and then determines the existence of basic users and describes the characteristics of available timing. Then, it determines the strategy set based on these characteristics and determines an optimal plan, finally coordinating the use of available timing based on the optimal plan.

Through the XG program, the US military has increased its spectrum efficiency 10–20 times. The program promotes the research and application of cognitive radio technology in the field of military communications. Whether it is conducting military exercises overseas or training at home, the issue of spectrum planning has always been a problem that the military field hopes to overcome. With cognitive radio technology, the military will no longer be limited to a static frequency plan, but can fundamentally meet changes in demand.

In Nov. 2004, the Institute of Electrical and Electronics Engineers (IEEE) 802.22 working group was formally established. Its main task is to develop and establish a set of regional network air interface standards based on cognitive radio technology that uses the temporarily idle spectrum of the existing TV frequency band for wireless communications. The standard is based on cognitive radio technology, which perceives and measures TV frequency bands, uses dynamic spectrum management technology, and finds a free spectrum for redistribution without interfering with the broadcasting TV spectrum.

In Feb. 2005, Simon Haykin published a landmark article on cognitive radio technology, “Cognitive radio: brain-empowered wireless communication” in IEEE Journal on Selected Areas in Communications, which strongly promoted international cognitive radio technology research [2].

Under the strong advocacy of the FCC, the US National Natural Science Foundation (NSF) funded the cognitive radio project as one of five subnets under the Global Network Interconnection Innovation Environment Project. The funded research content includes new cognitive radio technology validation, a physical layer adaptive wireless network protocol, a spectrum sharing method, dynamic spectrum measurement, and hardware implementation. With funding from the NSF, many university research institutes and research organizations such as the Software Defined Radio Forum have launched research into cognitive radio technology.

The field of wireless communications has undergone several changes, from fixed communications to mobile communications, from analog communications to digital communications, from hardware architecture to software programmable, and from blindness to cognition. The introduction of cognitive science has brought an epoch-making change to the field of wireless communications. Cognitive radio has transformed software radio from a blind executor of prefabricated programs into an intelligent agent in the radio field. It has the ability to meet user needs in various ways. At present, cognitive radio technology has become the research focus of international standardization organizations, research institutions and universities. Countries have invested large amounts of funds to set up research plans and research projects to conduct research into it.

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Voiceband Data Communications

Whitham D. Reeve, in Encyclopedia of Physical Science and Technology (Third Edition), 2003

I Applications and Networks

Data communication has long been with us, represented by written languages, semaphore signaling, and many other formats. Electrical data communication, including the concepts of multiplexing and efficient coding, was developed in the telegraph systems of the 19th century through the pioneering efforts of Samuel F. B. Morse. In the first half of the 20th century, teletype and telephoto services were implemented and became essential to the publishing industry. User-to-user data communication systems such as telex also became available as important commercial services. Electrical data communication became important to society in general with the beginning of the computer era in the 1960s.

In an information society, data are what carry information among people and machines. Word processing and document facsimile transmission, airline reservations and credit card authorization systems, automatic teller machines, personal computers and, of course, the world wide web all represent and process information as data. In some cases, these data are produced and used in one isolated location, but usually data are shuttled from one machine to another through a variety of communication facilities. If these activities take place within one building, as it might in a company office, a factory, or a local computing environment, a local area network (LAN) is likely to connect the equipment together. The interconnection of LANs by metropolitan area networks (MANs) and wide area networks (WANs) and the very rapid development of the internet show the important role of data communication in removing geographic constraints on the dissemination and use of electronic information.

Although many kinds of communication channels are used for data communication, the importance of the voiceband channel lies in the ubiquity of the switched telephone network and metallic twisted pair subscriber lines. When the need for communication from widely dispersed terminals to host computers became apparent in the 1960s, no widely available data networks with this kind of reach were available. For communicating data between nodes of an airline reservations network, calling in a credit card authorization from a point-of-sale terminal, or transferring data from a bank branch to a central computer, the most economical facilities were analog private lines and particularly switched access lines via the public switched telephone network (PSTN).

Communicating equipment such as terminals and computers produce digital signals designed to travel only a short distance to other equipment nearby. In order to connect equipment separated by longer distances, modems were developed that converted these native digital signals to waveforms capable of passing through analog passband telecommunication channels (Fig. 1). These channels had bandwidth, distortion, and noise characteristics much more accommodating to voice than to data. Telecommunication channels are most often switched, maintaining a fixed connection only for the duration of a call. This is not efficient for the “bursty” activity of a typical data terminal. Despite the later proliferation of specialized data networks with packet-switched communication for efficient sharing of communication links by bursty users, the need for access from locations not directly served by such networks called for voiceband data communication through the public network. The need for higher and higher data communication speeds concurrent with the development of the internet led to the development of dial-up modems that approach the maximum theoretical speed of the band-limited voiceband channel. Millions of modems are sold annually for use with personal computers and computer workstations. These must communicate through the subscriber lines for at least part of the connection to distant enterprise networks via remote access concentrators or internet service providers. Even if the entry node to a specialized data network or virtual private network (VPN) is relatively close to the network end of the subscriber line (Fig. 2), a voiceband data modem or digital subscriber line is needed.

FIGURE 1. Data transmission through a regular telecommunication channel. DTE—Data Terminal Equipment, DCE—Data Communication Equipment.

FIGURE 2. Data transmission over metallic twisted pair subscriber loops for data network access.

Users' equipment varies greatly in data format and speed. As technology and requirements evolve, so do modems. Many different types have been produced, as described in Section III.A; and fundamental distinction is made between asynchronous and synchronous communication. An asynchronous data stream does not have uniformly spaced pulse transitions (where a pulse represents the logic value of a bit or a group of bits); although, as Fig. 3 suggests, it often consists of bursts of uniformly spaced pulses that begin at arbitrary times. A burst may correspond to a particular character key that the user has just pressed. The receiving equipment is synchronized to each character burst, aided by “start” and “stop” indicators. A parity check bit (modulo 2 sum of the bits in a character representation) can be included in the character burst to allow the receiver to detect (but not correct) some transmission errors. Lower-cost (and lower-speed) terminals are often asynchronous, whereas more expensive (and higher-speed) equipment is synchronous. Asynchronous data communication between terminal and communicating equipment on an individual serial port normally is limited to around 56 or 112 kb/s. The standardization of data network interfaces to synchronous data formats and the availability of lower cost digital transmission and multiplex facilities have led to a broad use of synchronous terminals.

FIGURE 3. Asynchronous and synchronous data streams, illustrated for character burst traffic. In a synchronous data stream, there is no need for start and stop indicators to define timing because of uniform clocking of all pulse transitions.

Data communication in commercial applications is often characterized by a network of connections not just a single point-to-point circuit. Figure 4 illustrates the historic network architecture for a private inquiry-type, data communication network that was used in transactional applications, such as a reservations system. The links in this example are all permanently connected, voice grade private lines, leased from local exchange carriers (LECs) and interexchange carriers (IXCs). Cluster controllers coordinate the operation of several terminals at one location so they share the communication link appropriately. Concentrators combine lower-rate data streams into higher-rate streams for further savings on communication lines. Modems at each end of each communication link convert the baseband digital data streams at the terminal equipment interfaces to the continuous passband signals required on the voiceband communication circuits. A front-end communication processor at the host computer manages the network, leaving the host computer free for data processing functions. Although the links in this network are permanently connected, the traffic can be packet-switched if appropriate packet switches and formatters are installed by the network operators (for example, X.25 network with packet assembler–disassemblers, or PADs). Network architectures like this still exist, especially where the terminals are located in remote, rural areas served by analog satellite earth stations or analog microwave transmission systems.

FIGURE 4. Historic inquiry-type data communication network using modems, cluster controllers, concentrators, and a front-end processor.

The same network could well include dial-up terminals operating through ordinary switched loops from locations with insufficient traffic to justify a dedicated private line. This type of access is especially common for credit card authorization terminals in stores and restaurants and for access from personal computers and lap-top PCs to office computers and internet service providers for electronic mail (email) and other purposes. In modern applications and networks, the cluster controllers, communication processors, and analog backbone links shown in Fig. 4 have been replaced by remote access concentrators, routers, and digital links as shown in Fig. 5. In the latter, the remote access concentrator accepts incoming dial-up traffic or traffic from dedicated lines and concentrates it for presentation to a LAN router. The router performs authentication and other protocol functions and sends the data out an optical or electrical serial interface port to the digital communication network.

FIGURE 5. Modern digital network associated with inquiry-type, data communication network.

Data traffic, such as characters sent from a keyboard or a bulk file transfer between computers, is digital in origin, but not all data traffic originates in this way. Digital data streams can be derived from analog signals (for example, speech, fax, or voiceband modem signals), transmitted to distant locations with no degradation in quality, and converted back to analog signals. A device called a “CODEC” (COder-DECoder) converts the analog signals to and from a digital data stream (analog-to-digital, or A/D, and digital-to-analog, or D/A, respectively). Different coding techniques result in different data rates and conversion distortions. In circuit-switched networks (such as the PSTN), 64 kb/s pulse code modulation (PCM) and 16 and 32 kb/s adaptive differential PCM (ADPCM) commonly are used for high-quality telephone speech transmission. Other encoding schemes can compress digitized speech into data streams at rates from less than 2 kb/s to 16 kb/s but these usually have lower recovered quality and include significant processing delays. Nevertheless, these compression techniques are appropriate in many bandwidth-constrained applications, such as digital wireless networks and voice-over-packet applications. Even though the A/D conversion process results in distortion of the original analog signals, there are many advantages of digital transmission. These include (1) nearly perfect regeneration of digital signals regardless of the length of the circuit, (2) flexibility in mixing traffic of different media and service types, (3) ease of encrypting sensitive data, and (4) much more reliable and easily maintained transmission and multiplexing equipment.

Digital circuits carrying digitized analog traffic usually are internal to communication networks and not apparent to the end user. Digital loop carrier systems, access nodes, and primary multiplexers (channel banks) consolidate the outputs of a number of CODECs and combine the digitized analog signals in the telecommunication network. A variety of metallic twisted pair, microwave radio and optical fiber transmission systems, operating at data rates of 1.544 Mb/s (in the United States) and up, carry interleaved streams of digital data and digitized voice.

Although the high-speed links used in these carrier systems require much greater bandwidth than a voice grade channel, they use many of the same signal modulation and channel equalization techniques originally developed for the narrowband telephone circuit. In a typical situation:

A signal may originate in digital form at a terminal or PC

Be converted to analog form for transmission through a narrowband analog circuit by a voiceband modem

Be converted by a CODEC to a digital bit stream representing the analog modem signal

Be combined with other similar digital signals in a multiplexer to form a higher-speed aggregate signal within the network for transmission on a digital carrier system

Be demultiplexed and converted back to analog form for delivery to the other end of the channel by another CODEC

Be converted by another modem to a replica of the original digital data signal

The telecommunication networks of industrialized countries are evolving toward all-digital, multimedia networks that will eventually provide end-to-end carriage of data, digitized voice, and digitized video traffic. Some services involve integrated handling of different media and extensive user signaling to and through the network to setup a variety of calling and receiving options. The integrated services digital network (ISDN), a concept for a family of standard digital interfaces and services and having compatibility with existing analog and digital networks, continues to evolve. Voiceband data communication may eventually be superceded by end-to-end digital communication via an ISDN, but the principles of data communication developed for analog voice grade circuits will continue to find applications on the links and subscriber lines embedded in digital networks.

The transmission of information between a computer and other computers or the internet through the voiceband channel is a familiar application of modems. In addition to these familiar applications, low-speed voiceband modems, using standard protocols, are used to send caller number identification (CID or CND) and caller name (CNAM) from the central office switching system to a subscriber who subscribes to these features. The calling information is sent through the public telephone network (as in CID) or determined from a database embedded in the network (as in CNAM) and then transmitted to a box or telephone with a caller ID display on the called party's premises. These subscriber features are two of many Custom Local Area Signaling Services (CLASS®) offered via all modern switching systems.3

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The energy efficiency management system on ships using internet of things technology for reducing environmental pollution

Tien Anh Tran, in Recent Advancement of IoT Devices in Pollution Control and Health Applications, 2023

6.4.2 Experimental investigation: a case of a bulk carrier

The IoT technique is a main component of a wireless communication network. The installed sensors are to monitor the systematic platform, including the operational parameters of ships. The collected data is interconnected through the monitoring board system in both the engine control room and the bridge room of a ship (Fig. 6.6). The board system has been interconnected by the IoT model in this research. The big data will be collected and stored by the cloud server of IoT (Fig. 6.7).

Figure 6.6. The control console of M/V NSS HONESTY.

Figure 6.7. The flow meters (FMs) to measure the energy consumption of engines: (A) FM of main engine; (B) FM of diesel generator; (C) FM of marine boiler.

The sensors have been installed and have presented the energy consumption onboard the vessel. These sensors have been registered by the manufacturer. These sensors will be interconnected and incorporated with the IoT system model. The collected results have been recorded by the author and the seafarers on M/V NSS HONESTY. There are a total 16 voyages that have been conducted onboard the vessel. The proposed model has been installed both in the engine and bridge rooms. The collected values have been presented in the appendix, including Tables 6A.1–6A.3 for the main engine, the diesel generators, and the marine boiler.

The collected results have been compared with the experimental model onboard the vessel to evaluate the IoT proposed model in this research. The energy consumption of the main diesel engine has been recorded and presented in Fig. 6.8. The fuel consumption of the main diesel engine is different based on the various voyages. In reality, the values of IoT model are similar compared with the experimental model. It is significant that the remote energy consumption model is more reliable by utilizing the wireless communication network. Here, the energy consumption level is low at the voyages 3, 6, 10, and 13 with 36.5, 22.1, 44.5, and 37.1 tons, respectively.

Figure 6.8. Comparison values of energy consumption of main engine (unit: tons).

5wSimilarly, the energy consumption has been compared between the IoT model and the experimental model for the diesel generators at each certain voyage. The energy consumption is low at voyages 3, 6, 10, and 13 for IoT proposed model with 2.0, 1.0, 2.0, and 0.5 tons, respectively (Fig. 6.9). However, the energy consumption of the marine boiler is very low for all voyages. There is only one voyage, 16, with 0.7 tons, which is highest among the investigated voyages (Fig. 6.10).

Figure 6.9. Comparison values of energy consumption of diesel generators (unit: tons).

Figure 6.10. Comparison values of energy consumption of marine boiler (unit: tons).

The further comparison between the IoT model and the experimental model of the ship has been conducted through analyzing the relative relationship between the engines and devices. The intensive analysis has been summarized through the fitting curve tool. The collected results have been supported by MATLAB programming. The relative relationship has been presented in Figs. 6.11–6.14

Figure 6.11. The fuel oil (FO) energy consumption between main diesel engine versus diesel generator versus marine boiler.

Figure 6.12. The energy consumption between main diesel engine versus diesel generator versus marine boiler.

Figure 6.13. The energy consumption between diesel generator versus marine boiler.

Figure 6.14. The energy consumption between diesel generator versus marine boiler.

The energy consumption has been divided into two main types of fuel: heavy fuel oil or fuel oil (HFO, FO) and diesel oil (DO). Based on the IoT technique, the database has been collected through the sensors installed on the ships. Though the database analytics module, the curve fitting method has been employed to collect the results as well as evaluating the energy consumption.

Consequently, the energy consumption has been analyzed through evaluating the interactional relationship between the main diesel engine and diesel generator and marine boiler. In reality, the FO consumption of main diesel engine is the highest among other energy consumption sources. The energy consumption of main diesel engine could reach to over 700 tons each at voyage depending on the duration time. In this research, the object of study is a large ship with a long duration time. So, the collected results are significant through the IoT technique.

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Computing Platforms for the Internet of Things

Anantha D. Dhruva, ... B.S. Manoj, in Reference Module in Earth Systems and Environmental Sciences, 2023

Wi-Fi and Wi-Fi/SoftAP

Wi-Fi belongs to the IEEE 802.11 standard family of wireless communication protocols. In this chapter, we consider varied versions of the Wi-Fi family of protocols such as IEEE 802.11a, IEEE 802.11b, IEEE 802.11 g, and a combination of IEEE 802.11a/b/g/n/ac. Each of such protocols deals with the properties of the Wi-Fi module and its capabilities. Wi-Fi provides a communication range of 20 m for indoor and approximately 100 m for outdoor scenario (Ray, 2018). Software Access Point (SoftAP) is an IoT module capability to form an access point for network connectivity for Wi-Fi. Note that the SoftAP module was not originally designed as a router. A certain set of software transforms an IoT platform with SoftAP into a virtual router. The SoftAP capability is studied for various platforms in Section “Observations and Discussion”.

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Medical Biotechnology and Healthcare

A. Lalatsa, ... I.F. Uchegbu, in Comprehensive Biotechnology (Third Edition), 2011

5.46.3.3.1 Exploitation of Small Molecule Transporters

The exploitation of the various nutrients and hormones transports proteins and carrier systems at the BBB and is a potential strategy that may be utilized for delivery to the brain.

An excellent example of a drug that exploits an endogenous carrier is levodopa, a lipid-insoluble precursor of dopamine, used for the treatment of Parkinson‘s disease. The presence of the carboxyl and α-amino groups allows this drug to be transported across the BBB by the large neutral amino acid carrier. Suitable chemical modification of drugs enables their delivery across the BBB by the large neutral amino acid carrier (e.g., the anticancer drug d,l-2-amino-7-bis[(2-chloroethyl)amino]-1,2,3,4-tetrahydro-2-naphthoic acid).15 The carrier is specific for large neutral amino acids and it recognizes a carboxylic acid group and an amino group covalently linked to the same carbon atom, which is a characteristic of an α-amino group or a conformation that closely resembles this grouping (as in case of baclophen and gabapentin). A bulky hydrophobic group on the molecule is required to enable the molecule interaction with the cell membrane in order to align the amino and carboxylic groups to the active receptor site, thus excluding amino acids such as glycine and alanine.

Some carriers are very selective in their stereochemical substrate requirements. One example is the GLUT-1 carrier because only molecules that closely mimic d-glucose are transported. Glycosylated analogs of methionine5-enkephalin are transported via the hexose transporter GLUT-1,16 and endocytotic mechanisms have also been shown to be involved in the transport of glycosylated peptides. There are a number of examples of analgesia being enhanced on glycosylation of some peptide opioid agonists (e.g., glycoslated deltorphin and glycosylated leucine5-enkephalin amide and the l-serynyl-β-d-glucoside analogs of methionine5-enkephalin) and this is thought to be due to an increase in metabolic stability, reduced clearance, as well as improved BBB transport.

The hexose and large neutral amino acid carriers have the highest capacity and presently are the best candidates for delivery of substrates to the brain. Targeting peptides to a specific nutrient transporter will require good knowledge of both the peptide and the transporter.

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Medical Biotechnology and Healthcare

A. Lalatsa, ... I.F. Uchegbu, in Comprehensive Biotechnology (Second Edition), 2011

5.50.3.3.1 Exploitation of small molecule transporters

The exploitation of the various nutrient and hormones transport proteins and carrier systems at the BBB and is a potential strategy that may be utilized for delivery to the brain.

An excellent example of a drug that exploits an endogenous carrier is levodopa, a lipid-insoluble precursor of dopamine, used for the treatment of Parkinson’s disease. The presence of the carboxyl and α-amino groups allows this drug to be transported across the BBB by the large neutral amino acid carrier. Suitable chemical modification of drugs enables their delivery across the BBB by the large neutral amino acid carrier (e.g., the anticancer drug d,l-2-amino-7-bis[(2-chloroethyl)amino]-1,2,3,4-tetrahydro-2-naphthoic acid) [15]. The carrier is specific for large neutral amino acids and it recognizes a carboxylic acid group and an amino group covalently linked to the same carbon atom, which is a characteristic of an α-amino group or a conformation that closely resembles this grouping (as in case of baclophen and gabapentin). A bulky hydrophobic group on the molecule is required to enable the molecule interact with the cell membrane in order to align the amino and carboxylic groups to the active receptor site, thus excluding amino acids such as glycine and alanine.

Some carriers are very selective in their stereochemical substrate requirements. One example is the GLUT-1 carrier, because only molecules that closely mimic d-glucose are transported. Glycosylated analogs of methionine5-enkephalin are transported via the hexose transporter GLUT-1 [16], and endocytotic mechanisms have also been shown to be involved in the transport of glycosylated peptides. There are a number of examples of analgesia being enhanced on glycosylation of some peptide opioid agonists (e.g., glycoslated deltorphin and glycosylated leucine5-enkephalin amide and the l-serynyl-β – d-glucoside analogs of methionine5-enkephalin) and this is thought to be due to an increase in metabolic stability, reduced clearance, as well as improved BBB transport.

The hexose and large neutral amino acid carriers have the highest capacity and presently are the best candidates for delivery of substrates to the brain. Targeting peptides to a specific nutrient transporter will require good knowledge of both the peptide and the transporter.

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Radio-frequency imaging techniques for ionospheric, magnetospheric, and planetary studies

Shing F. Fung, ... Vikas Sonwalkar, in Understanding the Space Environment through Global Measurements, 2022

4.1 New technologies

The rapid advancement of radio technologies in digital radio industries such as in wireless communication and, especially, autonomous cars, has provided many unprecedented new capabilities. There are two major technologies that can potentially be used for radio space exploration: the digital transceiver and the matrix antenna. All of the radio technologies currently employed in space radio explorations can be replaced with some form of a combination of these new technologies which could lead to some fundamentally different thinking for space radio imaging instrumentation. The first and most important consequence of these new developments in the radio industry is that the digital transceivers have become highly integrated and extremely affordable. The development of transceivers is becoming mostly a software development process. These digital transceivers are compact with many transceivers built on a single chip. After the operational frequency and bandwidth are decided, transceiver development has become mainly a programming and debugging process to control the overall desired frequency and bandwidth so long as the transmission and reception are within this frequency band. The cost of this initial transceiver development is quite affordable and many high-tech companies can offer the development at very competitive prices. After a transceiver is developed, it can be copied with no additional costs other than the cost of the additional chips. It is economically possible to consider space systems with a large number of transceivers on single or multiple platforms. Transmission and reception of each transceiver in terms of the frequency steps, transmission/reception coordinating sequences, waveforms, as well as coordination among different transceivers can all be controlled by flight software development. The flight software can be modified even after the satellite is launched when new situations or needs are encountered. And with many transceivers, methods based on array or matrix concepts will be easily realized. For example, each element in the matrix can be treated as a pixel in an optical imager. Such transceivers, on many platforms, will greatly enhance space tomography and similar imaging concepts.

Antennas are the other key component other than the transceiver in a radio imager. The new radio technologies will change their appearance completely. If conventional space radio antennas have been electric dipole, magnetic loop, fishbone, or dish antenna, the new antenna appears as cells of a matrix, similar to a CCD matrix although much greater in size, such as the one shown in Fig. 4.52. This compact and lightweight antenna is known as the Tightly Coupled Dipole Array (TCDA). The antenna elements are built on the walls of each cell. When a radio wave propagates and reflects within a cell, interference occurs. Only a particular frequency band will be allowed to be transmitted and received. Therefore, the instrument designer can develop a TCDA antenna according to the frequency range of the radio imager. The bandwidth, measured by the ratio of the allowed frequency range to the center frequency, can be ultra wide. The cell size of each antenna element can be only 1/15 of the wavelength. A half-wavelength long antenna structure can accommodate eight cells. The total number of cells is determined by the required directionality of the transmitted beam and the spatial resolution of the received signal and is constrained by the size the satellite can accommodate. To limit the size of the antenna, high frequencies are preferred. This antenna technology is now mature and has been widely used in cellphone towers. More development is occurring in the autonomous car industry.

Figure 4.52. An example of a prototype 11 × 11-element TCDA (upper panel) as a dual-linear polarized phased array, and its two types of antenna elements (lower panels). The lower left panel shows a unit of transmission and reception, which comprises a printed circuit of built-in inductance, resistance, and capacitance; the lower right panel shows the receiver only unit. Combining the two provides the transmission and reception of the two polarizations of the electric field.

After Zhong, J., Johnson, A., Alwan, E.A., Volakis, J.L., 2019. Dual-linear polarized phased array with 9:1 bandwidth and 60 degrees scanning off broadside. IEEE Trans. Antenn. Propag. 67 (3), 1996–2001. https://dx.doi.org/10.1109/TAP.2019.2891607.

The antenna elements and matching circuits are printed on the walls of each cell as shown in the two lower panels of Fig. 4.52. The lower left panel, polarization 1, consists of a transmission and a reception antenna element which is connected to a transceiver. The lower right panel, polarization 2, consists of only a reception antenna. By combining the two elements, an instrument can transmit a linearly polarized wave and receive two orthogonal components of the signal in the plane of the antenna, i.e., make polarization measurements. This capability may be essential to detect the water/ice content of an imaging target. The system is referred to as a dual-linear polarized phased array. It can include a large number of dipole elements built compactly in two dimensions on a single board. With a large number of transmitters, the transmission power for each element can be reduced. The transmitted beam can be steered or scanned in different directions. The direction of the received signals can be determined. Each antenna element has an integrated tuning circuit printed on it, so that it can respond linearly in the frequency range of interest. The TCDA matrix antenna, with a large number of elements, is designed to be driven by a large number of transceivers (Song et al., 2021a).

The next generation of space radio instrumentation will likely be developed in two types of applications: (1) multiple platform systems for use, e.g., in space tomography, and (2) high-capacity synthetic aperture radar (SAR) for ground or ice penetrating radar (Song et al., 2021a). The latter application is likely to bring new science breakthroughs because surface features of planetary targets are relatively well observed with optical imagers. The new frontier is to discover what is beneath a planetary surface. The objectives of missions could range from purely scientific to more practical, such as the search for water and mineral resources and caves as shelters for astronauts. To penetrate the surface, the wavelength needs to be in the radio wave range as discussed in Section 2.1.5.

At first glance a matrix transceiver system appears extremely challenging to develop and complex to operate in space. Over the last decades, however, substantial experience has been accumulated in operating multiple transceivers in space and processing their data. The RPI on the IMAGE satellite operated 5 transmitters and 6 receivers (Reinisch et al., 2000). The tuner, narrow-band receiver, and transmitter (TNT) instrument (Reinisch et al., 2020) on the DSX satellite operates a dual-channel VLF transmitter and a narrow-band VLF-MF-HF receiver mated to an 80 m tip-to-tip dipole antenna (see, https://directory.eoportal.org/web/eoportal/satellite-missions/content/-/article/dsx). The transmitter automatically tunes each of the two channels to the antenna monopoles, individually, in order to compensate for the varying reactance of the electrically short antennas in the ambient plasma as DSX orbits the Earth. Synchronous operations of RF transceivers, for a multiplatform constellation of satellites, have been tested on the ground in Europe with 6 digisondes (Reinisch et al., 2018). The additional capability of individually auto-tuned multifrequency transmissions has been tested with the TNT. The number of platforms and transceivers is expected to increase substantially on future missions.

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Prospects and challenges for the green hydrogen market

Arcílio B.S. Semente, ... Diogo M.F. Santos, in Solar-Driven Green Hydrogen Generation and Storage, 2023

3.5 Liquid organic hydrogen carriers

Another alternative option that has raised considerable interest for storing hydrogen is liquid organic hydrogen carrier (LOHC) systems. They consist of a pair of one hydrogen-lean compound and one hydrogen-rich compound. Hydrogen is stored chemically by reacting with the hydrogen-lean compound in a catalytic hydrogenation reaction, and then the reverse process releases hydrogen. One great benefit of using LOHC systems is that hydrogen can be stored for a very long time without self-discharge, which is interesting for seasonal energy storage. The process is reversible and offers good kinetics for the dehydrogenation/hydrogenation processes, and only hydrogen is released [22,29].

Some of the LOHC compounds most studied include benzene (C6H6) and cyclohexane (C14H12), toluene, and methylcyclohexane. Cyclohexane has a hydrogen storage capacity of 7.19 wt%, but its practical use becomes limited due to its low boiling point. In addition, its dehydrogenation product is benzene, which is carcinogenic.

The MTH (methylcyclohexane-toluene-hydrogen) system has been widely studied and researched. Methylcyclohexane presents 6.2 wt% of storage capacity and is liquid at room temperature. The dehydrogenation process of methylcyclohexane to toluene is relatively easier than the previous LOHC compound. In addition, methylcyclohexane has a boiling point (100.9°C) close to water's boiling point and presents a density and viscosity close to gasoline. These gasoline-like characteristics could make them be used in existing infrastructures built for gasoline with the appropriate modifications and changes. It has to be noted that methylcyclohexane dehydrogenation presents an equilibrium conversion of almost 100% only at 325°C at 1 bar.

Green hydrogen stored in LOHC systems is a tradable, storable, and transportable form of renewable energy that could embrace the ambitions of striving for a more sustainable future [22,29].

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URL: https://www.sciencedirect.com/science/article/pii/B9780323995801000212