Long/Short 훈련심볼을 이용하는 개선된 채널추정기법에 의한 IEEE 802.11a 무선 LAN 시스템의 성능 개선

곽재민,정해원,조성준,이형호 한국항행학회 2002 韓國航行學會論文誌 Vol.6 No.3

본 논문에서 IEEE 802.11a 의 규격에 따라 OFDM 무선 LAN 모뎀과 프레임 포맷을 구성하여 시뮬레이션에 의해 BER 성능을 분석하고 수정된 채널 예측 알고리즘을 적용하여 채널 예측 성능이 개선됨을 보인다. 채널 예측에 이용되는 실내 무선채널로서는 AWGN과 TDL모델을 적용한 지연확산채널을 고려한다. 우선 AWGN환경에서 규격에 제시된 전송속도 및 부호율에 따른 OFDM 무선 LAN 시스템의 성능을 분석한다. 다음으로 실내무선 채널 환경에서 채널추정이 불완전한 경우에 대해, 기존의 채널추정방식으로서 프리앰블 내의 2개의 Long 훈련 심볼을 이용하여 채널을 추정하는 경우에 대한 성능을 분석하고, 수수정된 채널 추정기법으로는 IEEE 802.11a의 프리앰블 구조를 변경하지 않으면서 Long 훈련심볼뿐만 아니라 전체 10개의 Shot 훈련심볼 중 8개의 훈련심볼들을 채널추정에 부가적으로 사용하는 방식을 채용한 경우의 성능을 분석하여 기존의 방식과 비교한다. 시뮬레이션 결과의 분석으로부터 수정된 채널 추정방식을 적용하는 경우, 규격에 정의된 프리앰블 구조의 변경없이도 잡음을 억제하는 효과를 향상시킴으로써 채널추정오차가 감소되어 채널추정성능이 개선됨을 확인하였다. In this paper, the BER performance of IEEE 802.11a OFDM WLAN system is obtained by simulation and it is shown that the proposed modified channel estimation algorithm improves the channel estimation performance of the system. The wireless channel used in channel simulation includes AWGN and delay spread channel implemented by TDL model. At first, the performance of OFDM WLAN system according to data rate and coding rate defined in standard is evaluated in AWGN channel. Then, imperfect channel estimation in indoor wireless channel is considered. After the performance of conventional channel estimation scheme using only two long training symbols is evaluated, and that of proposed modified channel estimation scheme using additional 8 short training symbol is compared with it. From the simulation results, it is shown that modified channel estimation scheme provides reduced channel estimation error and improves the channel estimation performance due to noise averaging effect with the same preamble format as defined in specification.

[P5-73] Purification of Transglutaminase from Streptomyces pla-tensis YK-2 and Improvement of Strains

Hae Jung Kwak,Hee-Sun Ko,Dong Hee Kang,Ho Kyung Bae,Ji Yeon Ryu,Sae Mi Lee,Na Rae Lee,Yuen Jung Lee,Hyun Soo Kim 한국식품영양과학회 2009 한국식품영양과학회 학술대회발표집 Vol.2009 No.11

Comparison of Physicochemical and Sensory Properties between Cholesterol-removed Gouda Cheese and Gouda Cheese during Ripening

Jung, Ho-Jung,Ko, Eun-Jung,Kwak, Hae-Soo Asian Australasian Association of Animal Productio 2013 Animal Bioscience Vol.26 No.12

This study was performed to compare physicochemical and sensory properties of cholesterol-removed Gouda cheese (CRGC) and Gouda cheese made in the laboratory during ripening. Composition, short-chain free fatty acids (SCFFA), texture, color, and sensory properties were measured. In chemical composition analyses, moistures were significantly different between control cheeses (42.86%) and sample cheese (48.32%) (p<0.05). But fat and protein in the control and the sample were 32.77, 22.45 and 31.35, 20.39%, respectively, and were not significantly different (p>0.05). The amount of cholesterol in control was 82.52 mg/100 g and the percentage of cholesterol removal was 90.7%. SCFFA increased gradually during ripening and its level of CRGC increased and significantly different from that of control (p<0.05). The texture, hardness, gumminess, and chewiness were significantly increased, but cohesiveness and springiness were not increased in both cheeses during ripening periods (p>0.05). In comparison of the control and sample cheeses, hardness, and springiness were not significantly different, but cohesiveness, gumminess, and chewiness were different (p<0.05). In color measurement, all color values were not different between CRGC and control (p>0.05). However, $L^*$ value decreased, while $a^*$ and $b^*$ values tended to increase significantly (p<0.05). In sensory properties, appearance, aroma, flavor and taste, and texture were significantly increased except buttery and nutty in aroma and sweetness in taste in both cheeses, and were not significantly different between the control and sample cheeses during ripening (p>0.05). Therefore, this study suggests that the quality of cholesterol-removed Gouda cheese is not different from the control cheese.

The Factors Affecting Attitudes Toward HSDPA Service and Intentionto Use: A Cross-Cultural Comparison between Asia and Europe

Hae Sung Jung,Jong Kuk Shin,박민숙,Hong-Seob Jung,Graham Hooley,Nick Lee,Hyokjin Kwak,Sung Hyun Kim 한국마케팅과학회 2009 마케팅과학연구 Vol.19 No.4

HSDPA (High-Speed Downlink Packet Access) is a 3.5-generation asynchronous mobile communications service based on the third generation of W-CDMA. In Korea, it is mainly provided in through videophone service. Because of the diffusion of more powerful and diversified services, along with steep advances in mobile communications technology, consumers demand a wide range of choices. However, because of the variety of technologies, which tend to overflow the market regardless of consumer preferences, consumers feel increasingly confused. Therefore, we should not adopt strategies that focus only on developing new technology on the assumption that new technologies are next-generation projects. Instead, we should understand the process by which consumers accept new forms of technology and devise schemes to lower market entry barriers through strategies that enable developers to understand and provide what consumers really want. In the Technology Acceptance Model (TAM), perceived usefulness and perceived ease of use are suggested as the most important factors affecting the attitudes of people adopting new technologies (Davis 1989; Taylor and Todd 1995; Venkatesh 2000; Lee et al. 2004). Perceived usefulness is the degree to which a person believes that a particular technology will enhance his or her job performance. Perceived ease of use is the degree of subjective belief that using a particular technology will require little physical and mental effort (Davis, 1989; Morris and Dillon 1997; Venkatesh 2000). Perceived pleasure and perceived usefulness have been shown to clearly affect attitudes toward accepting technology (Davis et al. 1992). For example, pleasure in online shopping has been shown to positively impact consumers' attitudes toward online sellers (Eighmey and McCord, 1998; Mathwick, 2002; Jarvenpaa and Todd 1997). The perceived risk of customers is a subjective risk, which is distinguished from an objective probabilistic risk. Perceived risk includes a psychological risk that consumers perceive when they choose brands, stores, and methods of purchase to obtain a particular item. The ability of an enterprise to revolutionize products depends on the effective acquisition of knowledge about new products (Bierly and Chakrabarti 1996; Rothwell and Dodgson, 1991). Knowledge acquisition is the ability of a company to perceive the value of novelty and technology of the outside (Cohen and Levinthal 1990), to evaluate the outside technology that has newly appeared (Arora and Gambaradella, 1994), and to predict the future evolution of technology accurately (Cohen and Levinthal 1990). Consumer innovativeness is the degree to which an individual adopts innovation earlier than others in the social system (Lee, Ahn, and Ha 2001; Gatignon and Robertson 1985). That is, it shows how fast and how easily consumers adopt new ideas. Innovativeness is regarded as important because it has a significant effect on whether consumers adopt new products and on how fast they accept new products (Midgley and Dowling 1978; Foxall 1988; Hirschman 1980). We conducted cross-national comparative research using the TAM model which empirically verified the relationship between the factors that affect attitudes - perceived usefulness ease of use perceived pleasure perceived risk innovativeness and perceived level of knowledge management - and attitudes toward HSDPA service. We also verified the relationship between attitudes and usage intention for the purpose of developing more effective methods of management for HSDPA service providers. For this research 346 questionnaires were distributed among 350 students in the Republic of Korea. Because 26 of the returned questionnaires were inconsistent or had missing data 320 questionnaires were used in the hypothesis tests. In UK 192 of the total 200 questionnaires were retrieved and two incomplete ones were discarded bringing the total to 190 questionnaires used for statistical analysis. The results o... HSDPA (High-Speed Downlink Packet Access) is a 3.5-generation asynchronous mobile communications service based on the third generation of W-CDMA. In Korea, it is mainly provided in through videophone service. Because of the diffusion of more powerful and diversified services, along with steep advances in mobile communications technology, consumers demand a wide range of choices. However, because of the variety of technologies, which tend to overflow the market regardless of consumer preferences, consumers feel increasingly confused. Therefore, we should not adopt strategies that focus only on developing new technology on the assumption that new technologies are next-generation projects. Instead, we should understand the process by which consumers accept new forms of technology and devise schemes to lower market entry barriers through strategies that enable developers to understand and provide what consumers really want. In the Technology Acceptance Model (TAM), perceived usefulness and perceived ease of use are suggested as the most important factors affecting the attitudes of people adopting new technologies (Davis 1989; Taylor and Todd 1995; Venkatesh 2000; Lee et al. 2004). Perceived usefulness is the degree to which a person believes that a particular technology will enhance his or her job performance. Perceived ease of use is the degree of subjective belief that using a particular technology will require little physical and mental effort (Davis, 1989; Morris and Dillon 1997; Venkatesh 2000). Perceived pleasure and perceived usefulness have been shown to clearly affect attitudes toward accepting technology (Davis et al. 1992). For example, pleasure in online shopping has been shown to positively impact consumers' attitudes toward online sellers (Eighmey and McCord, 1998; Mathwick, 2002; Jarvenpaa and Todd 1997). The perceived risk of customers is a subjective risk, which is distinguished from an objective probabilistic risk. Perceived risk includes a psychological risk that consumers perceive when they choose brands, stores, and methods of purchase to obtain a particular item. The ability of an enterprise to revolutionize products depends on the effective acquisition of knowledge about new products (Bierly and Chakrabarti 1996; Rothwell and Dodgson, 1991). Knowledge acquisition is the ability of a company to perceive the value of novelty and technology of the outside (Cohen and Levinthal 1990), to evaluate the outside technology that has newly appeared (Arora and Gambaradella, 1994), and to predict the future evolution of technology accurately (Cohen and Levinthal 1990). Consumer innovativeness is the degree to which an individual adopts innovation earlier than others in the social system (Lee, Ahn, and Ha 2001; Gatignon and Robertson 1985). That is, it shows how fast and how easily consumers adopt new ideas. Innovativeness is regarded as important because it has a significant effect on whether consumers adopt new products and on how fast they accept new products (Midgley and Dowling 1978; Foxall 1988; Hirschman 1980). We conducted cross-national comparative research using the TAM model which empirically verified the relationship between the factors that affect attitudes - perceived usefulness ease of use perceived pleasure perceived risk innovativeness and perceived level of knowledge management - and attitudes toward HSDPA service. We also verified the relationship between attitudes and usage intention for the purpose of developing more effective methods of management for HSDPA service providers. For this research 346 questionnaires were distributed among 350 students in the Republic of Korea. Because 26 of the returned questionnaires were inconsistent or had missing data 320 questionnaires were used in the hypothesis tests. In UK 192 of the total 200 questionnaires were retrieved and two incomplete ones were discarded bringing the total to 190 questionnaires used for statistical analysis. The results of the o...

Synthesis of 7-Hydroxy-4-Oxo-4H-Chromene- and 7-Hydroxychroman-2-Carboxylic Acid N-Alkyl Amides and Their Antioxidant Activities

Kwak, Jae-Hwan,Kang, Hae-Eun,Jung, Jae-Kyung,Kim, Hwa-Jung,Cho, Jung-Sook,Lee, Hee-Soon The Pharmaceutical Society of Korea 2006 Archives of Pharmacal Research Vol.29 No.9

A series of 7-hydroxy-4-oxo-4H-chromene- (3a - h) and 7-hydroxychroman-2-carboxylic acid N-alkyl amides (4a - g) were synthesized and their antioxidant activities were evaluated. While compounds 3a - h were less active, compounds 4a - g exhibited more potent inhibition of lipid peroxidation initiated by $Fe^{2+}$ and ascorbic acid in rat brain homogenates. Among them, 7-hydroxychroman-2-carboxylic acid N-alkylamides (4e - g) bearing nonyl, decyl, and undecyl side chain exhibited 3 times more potent inhibition than trolox (1).

The Factors Affecting Attitudes Toward HSDPA Service and Intention to Use: A Cross-Cultural Comparison between Asia and Europe

Jung, Hae-Sung,Shin, Jong-Kuk,Park, Min-Sook,Jung, Hong-Seob,Hooley, Graham,Lee, Nick,Kwak, Hyok-Jin,Kim, Sung-Hyun Korean Academy of Marketing Science 2009 마케팅과학연구 Vol.19 No.4

HSDPA(高速下行分组接入)是在第三代的W-CDMA技术基础上的3.5代移动通信异步服务. 在韩国, 它主要是通过提供可视电话服务. 由于更强大和多元化的服务扩散, 随着移动通信技术迅速的进步, 消费者需要更多的选择. 然而, 由于各种技术, 不论消费者偏好往往会溢出市场, 消费者感到越来越迷惑. 因此, 我们不应该采取只注重发展假设是下一代新技术项目的战略相反, 我们应该了解消费者接受新的形式和技术的过程, 通过制定战略, 使开发人员能够理解并提供消费者真正想要的, 从而降低进入市场的障碍. 在技术接受模型(TAM)中, 感知到的有用性和使用的简单性被认为是影响人们接受新技术的态度的最重要因素(Davis, 1989; Taylor and Todd, 1995; Venkatesh, 2000; Lee et al., 2004). 感知到的有用性是一个人相信某种特定的技术能提高他或她工作绩效的程度. 感知易用性是主观认为使用某种特定技术不需要太多体力和精力的付出的程度(Davis, 1989; Morris and Dillon, 1997; Venkatesh, 2000). 感知的愉悦性和感知的有用性已经被清楚的证明对接受技术的态度有影响(Davis et al., 1992). 比如, 网上购物的愉悦性已经表现出对消费者对网上商家的态度有积极的影响(Eighmey and McCord, 1998; Mathwick, 2002; Jarvenpaa and Todd, 1997). 消费者的感知风险是一种主观风险. 这种风险和客观可能的风险是有显著区别的. 感知风险包括心理上的风险, 这是当消费者为某一特定物品而选择品牌, 商店和购买方式时所感知到的. 企业革新产品的能力取决于有效的获得有关新产品的知识(Bierly and Chakrabarti, 1996; Rothwell and Dodgson, 1991). 知识获取是公司感知外界新事物和技术的价值的能力(Cohen and Levinthal, 1990); 是公司评估外界最新的技术的能力(Arora and Gambaradella, 1994); 是公司正确预测这项科技对未来革新的能力(Cohen and Levinthal, 1990). 消费者创新是一种在社会体系中比其他人更早接受创新的程度(Lee, Ahn, and Ha, 2001; Gatignon and Robertson, 1985). 也就是说, 它显示了消费者如何快速、方便地接受新的思路. 创新被认为是重要的, 因为它对消费者是否接受新产品和他们多快接受新产品有显著的影响(Midgley and Dowling, 1978; Foxall, 1988; Hirschman, 1980). 我们用技术接受模型来进行跨国家的研究比较, 此模型实证验证了影响态度的因素-感知有用性, 易用性, 感知愉悦, 感知风险, 创新和感知的知识管理水平-和对HSDPA服务的态度之间的关系. 我们为HSDPA服务提供商开发更有效的管理方法还验证了态度和使用意图之间的关系. 在本研究中, 我们在韩国350名学生中分发了346份问卷调查. 由于其中26份收回的问卷时不完整的或者有缺失数据, 所以在假设检验时320份问卷被使用. 在英国, 200份问卷收回了192份, 舍弃了两份不完整的之后, 总共有190份问卷用于统计分析中. 整体模型的分析结果如下: 韩国, x2=333.27(p=0.0), NFI=0.88, NNFI=0.88, CFI=0.91, IFI=0.91, RMR=0.054, GFI=0.90, AGFI=0.84; 英国, x2=176.57(p=0.0), NFI=0.88, NNFI=0.90, CFI=0.93, IFI=0.93, RMR=0.062, GFI=0.90, AGFI=0.84. 在韩国消费者中, 从有关影响HSDPA服务的使用意图和态度之间的关系的假设检验的结果中, 感知的有用性, 易用性, 乐趣, 知识管理的高水平和促进创新对HSDPA移动手机的态度有积极的影响. 然后, 易用性和感知的乐趣对HSDPA服务的使用意图没有直接的影响. 这可能是因为在日常生活中使用视频电话还不是必需的这一现实. 而且消费者对HSDPA视频电话的态度和使用意图有直接的关系, 这些态度包括感知的有用性, 易用性, 乐趣, 知识管理的高水平和创新. 这些关系构成了购买意图

치자 열매 추출물의 Tyrosinase 효소활성 저해 및 Melanogenesis 억제 효과

곽정훈(Jung-Hoon Kwak),김용해(Yong-Hae Kim),장해룡(Hae-Ryong Chang),박철우(Chul-Woo Park),한영환(Yeong-Hwan Han) 한국생물공학회 2004 KSBB Journal Vol.19 No.6

Recovery of Cholesterol from the β-Cyclodextrin-Cholesterol Complex Using Immobilized Cyclomaltodextrinase of Alkalophilic Bacillus sp. KJ 133

Kwon, Ho Jeong,Jung, Hye Jin,Kwak, Hae Soo 한국미생물 · 생명공학회 2001 Journal of microbiology and biotechnology Vol.11 No.4

A new combined method including the enzymatic hydrolysis of β-cyclodextrin (β-CD) and solvent extraction of cholesterol from the hydrolyzed mixture was developed to recover cholesterol from a β-CD-cholesterol complex prepared from dairy products, such as cream, milk, and cheese. Cyclomaltodextrinase (cyclomaltodextrin dextrin hydrolase, EC 3.2.1.54, CDase) prepared from alkalophilic Bacillus sp. KJ 133 hydrolyzed the β-CD of the β-CD-cholesterol complex, and then, free cholesterol was efficiently extracted from the hydrolyzed mixture by a nonpolar solvent such as ethyl acetate. To increase the stability of free CDase, immobilized CDase was developed using sodium alginate as a carrier. The immobilized CDase showed a high recovery yield of cholesterol in a time-dependent manner compared to the free CDase. A gas chromatography analysis showed that more than 70% of cholesterol was recovered from the β-CD-cholesterol complex of cream by the immobilized CDase, whereas only 3% and 29% of cholesterol were recovered when the solvent extraction and free CDase treatment were used, respectively. The cholesterol recovered can be used as a raw material for steroid synthesis. Furthermore, this method can be an efficient way to recover cholesterol or other organic compounds that are bound in a β-CD-cholesterol or -organic compound complex.

Molecular Characterization of Five Potyviruses Infecting Korean Sweet Potatoes Based on Analyses of Complete Genome Sequences

Kwak, Hae-Ryun,Kim, Jaedeok,Kim, Mi-Kyeong,Seo, Jang-Kyun,Jung, Mi-Nam,Kim, Jeong-Soo,Lee, Sukchan,Choi, Hong-Soo The Korean Society of Plant Pathology 2015 Plant Pathology Journal Vol.31 No.4

Sweet potatoes (Ipomea batatas L.) are grown extensively, in tropical and temperate regions, and are important food crops worldwide. In Korea, potyviruses, including Sweet potato feathery mottle virus (SPFMV), Sweet potato virus C (SPVC), Sweet potato virus G (SPVG), Sweet potato virus 2 (SPV2), and Sweet potato latent virus (SPLV), have been detected in sweet potato fields at a high (~95%) incidence. In the present work, complete genome sequences of 18 isolates, representing the five potyviruses mentioned above, were compared with previously reported genome sequences. The complete genomes consisted of 10,081 to 10,830 nucleotides, excluding the poly-A tails. Their genomic organizations were typical of the Potyvirus genus, including one target open reading frame coding for a putative polyprotein. Based on phylogenetic analyses and sequence comparisons, the Korean SPFMV isolates belonged to the strains RC and O with >98% nucleotide sequence identity. Korean SPVC isolates had 99% identity to the Japanese isolate SPVC-Bungo and 70% identity to the SPFMV isolates. The Korean SPVG isolates showed 99% identity to the three previously reported SPVG isolates. Korean SPV2 isolates had 97% identity to the SPV2 GWB-2 isolate from the USA. Korean SPLV isolates had a relatively low (88%) nucleotide sequence identity with the Taiwanese SPLV-TW isolates, and they were phylogenetically distantly related to SPFMV isolates. Recombination analysis revealed that possible recombination events occurred in the P1, HC-Pro and NIa-NIb regions of SPFMV and SPLV isolates and these regions were identified as hotspots for recombination in the sweet potato potyviruses.

Yogurt 의 향미성분과 분석기술

곽해수,장은정 한국유가공기술과학회 2000 Journal of Dairy Science and Biotechnology (JMSB) Vol.18 No.1

Consumers primarily consider flavor when they take yogurt. Recent researches on yogurt flavor production its analytical technique have been extensively developed. These studies have provided a better understanding on the role of starter culture microorganisms on flavor formation and degradation. Yogurt volatile flavor compounds produced by the lactic cultures include acetaldehyde, diacetyl, ethanol and organic acid. Among them, acetaldehyde is recognized as a principal flavor component. since yogurt contains a delicate and low intense flavor, mild sample isolation techniques and sensitive identification means might be used. This paper attempts to discuss recent findings in yogurt flavor and to describe the application of yogurt flavor separation techniques. The section on practical aspects of culture selection based on flavor compound production and flavor analysis is also included.